If you're using flakes and since lemmy is packaged in nixpkgs, you can spawn a dev shell with:
nix develop nixpkg#lemmy-server
If you're using flakes and since lemmy is packaged in nixpkgs, you can spawn a dev shell with:
nix develop nixpkg#lemmy-server
This gives you a build environment for lemmy, see the example. You can clone upstream and use that shell to build lemmy. Quite convenient to test quick changes. However, that won't help distributing your fork.