I’ve tried looking up guides, and it’s not a simple task, especially if you’re reverse engineering somebody else’s script. If I can just run it in a bootable container as if I was using a typical mutable system, that’s something pretty much everybody can do.

But I agree, there’s a few tools that make building RPMs and flatpaks easier, and it can be done. It’s just that the learning curve is steeper, and that is going to keep certain people away from immutable distros.