The task currently uses Debian 11 Bullseye, which will be EOL in ~2024-07, according to https://wiki.debian.org/DebianReleases#Production_Releases
So it would be good to bump either now or latest in 6 months.
Ideally the ARM CI task uses the version of GCC that guix uses to cross compile, which is currently GCC 10 and Debian Bookworm ships with GCC 12, so I'll leave this in draft for now. See also https://packages.debian.org/bookworm/gcc-arm-linux-gnueabihf