[Solved] This maybe a strange question but can I run a Linux app in a separate container/sandbox? Without its dependencies bloating my host OS?

IIRC that's the whole point of flatpak, snap and appimage

Docker can probably do it too, distrobox puts a useful wrapper on that

Nix does that kind of, nix packages aren't isolated in that they can't access resources on your system but all dependencies are stored in the nix store, hashed and isolated from eachother, and wiped when you collect garbage