Hi!  It seems souring /etc/profile.d/guix.sh can return non-zero due to
this line:

[ -L $GUIX_PROFILE ] || return

This happens if the first command fail in a pipefail situation.  I
suppose the intention was to exit with error code 0 if GUIX_PROFILE
isn't a symlink?  If so, see attached patch, also pushed here:

https://salsa.debian.org/debian/guix/-/merge_requests/4

/Simon