Comment 21 for bug 1823790

In my case the issue with using Ubuntu 20.04 as a container host appears to have come down to the use of the F, or "fix binary", flag by binfmnt_misc:

# cat /proc/sys/fs/binfmt_misc/qemu-aarch64
enabled
interpreter /usr/bin/qemu-aarch64-static
flags: OCF
offset 0
magic 7f454c460201010000000000000000000200b700
mask ffffffffffffff00fffffffffffffffffeffffff

This appears to be new in Ubuntu 20.04 relative to 18.04 and results in the qemu-user-static binaries being loaded and locked into memory _when the package is installed_.

Therefore, what I observed as a regression of the issue was actually just the packaged binaries now taking precedence over patched versions that I had built and copied into place.

Ubuntu 20.04 ships QEMU 4.2. Using the QEMU 5.1 packages from Debian Bullseye allows SystemD to run in a foreign architecture container without spinning in a loop:

  https://packages.debian.org/bullseye/qemu-user-static