If this is on Debian 12 I think the issue is that the default storage backend is VFS rather than Overlay, which burnt me as well as it is REALLY inefficient. Look up how to find out what you’re using and change it if that’s it. After doing that it’s been really good for me :)

Yeah, I get that. I was daily driving Guix for quite a long time and really enjoyed it. As I understand it shares a lot of code with Nix. It’s just been a bit hard to integrate with a lot of the software I run due to it not being compatible with the traditional filesystem hierarchy. This is obviously a selling point for Nix/Guix as it frees it to try new ideas, but makes it harder for me to run my music production software for example, which I can’t run in flatpak officially and since it Just Works™ on Debian, I’m happy with it. Maybe I’ll get into it sometime again as the community seems to have grown a lot, and I’ve looked into running Nix on top of my Debian install.