As per our discussion, I have temporarily rustc in mantic-proposed to universe:

$ change-override -c universe -S rustc -s mantic-proposed 
Override component to universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic: main/misc -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/extra/100% -> universe
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: main/doc/extra/100% -> universe
cargo-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: main/doc/extra/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: main/libs/optional/100% -> universe
libstd-rust-1.68 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: main/libs/optional/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: main/libdevel/extra/100% -> universe
libstd-rust-dev 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: main/libdevel/extra/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/optional/100% -> universe
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/optional/100% -> universe
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/optional/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: main/doc/extra/100% -> universe
rust-doc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: main/doc/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/extra/100% -> universe
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/extra/100% -> universe
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/extra/100% -> universe
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: main/devel/extra/100% -> universe
rustc 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: main/devel/extra/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64: universe/devel/optional/100% -> universe
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x: universe/devel/optional/100% -> universe
Override [y|N]? y
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
cargo 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rust-all 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rust-clippy 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rust-gdb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rust-lldb 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rust-src 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic amd64 remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic arm64 remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic armhf remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic i386 remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic ppc64el remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic riscv64 remained the same
rustfmt 1.68.0+dfsg0ubuntu1-0ubuntu1 in mantic s390x remained the same
36 publications overridden; 49 publications remained the same.