> I think we now have something that works well.

It doesn't work.

# ls -l /nix/var/nix/profiles/per-user/root/

[...]

guix-profile -> /nix/var/nix/profiles/per-user/root/guix-profile-16-link
guix-profile-15-link -> /nix/store/05gws0ijjf8bczrrsi8mrhh16xii0vis-user-environment
guix-profile-16-link -> /nix/store/aslx7hfjzkzjr73hbyk25997aap3avcb-user-environment

[...]

# ./pre-inst-env guix-package --roll-back
error: no previous profile; not rolling back

# ./pre-inst-env guix-package --roll-back
      -p /nix/var/nix/profiles/per-user/root/guix-profile
error: no previous profile; not rolling back

I'll try to investigate later.

Nikita