

No, you are getting the correct Lutris derivation, but it seems like you can’t override buildFHSEnv in this way (unlike a regular derivation) which is unfortunate. Looking at it again the package takes an extraLibraries parameter (but it’s a function taking a pkgs argument and producing a list, not a bare list). In principle this should work:
home.packages = with pkgs; [
(lutris.override {
extraLibraries = pkgs: [ # shadows the other pkgs!
(pkgs.runCommand "steamrun-lib" { } ''
mkdir "$out"
ln -s "${pkgs.steam-run.fhsenv}"/usr/lib64 "$out"/lib
'')
];
})
];
But it actually fails because both steam-run and lutris provide /usr/lib64/ld-linux.so.2 leading to a name collision. So unfortunately it seems the idea of just adding the steam-run env to Lutris doesn’t quite work…
You could instead try something like this:
home.packages = with pkgs; [
(lutris.override {
extraLibraries = pkgs: with pkgs; [
glibc
libxcrypt
libGL
# ... other libs in steam-run.fhs but not in the lutris FHS env
];
})
];
Which library the problem game actually needs is anyone’s guess. That information might show up somewhere in the logs, or maybe ldd could tell you… but the signal to noise ratio probably won’t be very good.

As far as I’m aware Home Manager doesn’t set PATH at all, though the Nix installer does. I’m not sure where it adds to the PATH, it might edit
/etc/profileor something like that. You should be able to change it since you’re not on NixOS.Alternatively this should also do the trick, although it’s a bit ugly: