Comment 57 for bug 1926938

@DanglingPointer #55

"If you want to stay with Ubuntu 20.04 LTS with latest stable mainline, you'll need to build it."

not true... if not have external kernel modules (ex. using dkms builded module for VirtualBox, Nvidia, tlp, wifi driver for card not supported by mainline, etc..) then only not install problematic linux-headers-5.13.2-051302-generic package

in other case, is possible install it via "workaround"...

# only unpack without install/configure
dpkg --unpack linux-headers-5.13.2-051302-generic_5.13.2-051302.202107141437_amd64.deb

in /usr/src/linux-headers-5.13.2-051302-generic/ replace this files:
"scripts/basic/fixdep tools/objtool/fixdep tools/bpf/resolve_btfids/fixdep scripts/mod/modpost tools/objtool/objtool"
from: linux-headers-5.11.16-051116-generic_5.11.16-051116.202104211235_amd64.deb
(latest headers package version before switch to glibc 2.33)

# configure it with ignoring libc6 depends:
dpkg --configure --ignore-depends=libc6 linux-headers-5.13.2-051302-generic

# fake libc6 depend version in dpkg status file
sed "/Depends: linux-headers-5.13.2-051302, libc6/s/libc6 (>= 2...)/libc6 (>= 2.31)/" -i /var/lib/dpkg/status

i using this workaround with my own tool for installing "Ubuntu Mainline Kernel" on all my Xubuntu 20.04 machines and without problem from 5.11.17 to latest 5.13.2 ;-)