I recently followed https://www.arthurkoziel.com/installing-nixos-on-a-macbookpro/ to install NixOS on a macbookpro5,1 (from 2008). OSX hasn't supported that hardware since El Capitan and it was incredibly slow even then.
With Nix it works, but I'm frequently running into issues similar to https://askubuntu.com/questions/1114612/rcu-sched-self-detected-stall-on-cpu-watchdog-bug-soft-lockup-cpu3-stuck. The first 3 times I tried logging in after the install it hung after accepting the password. It was just logging the rcu stall error every few seconds, not responding to any keys. I was able to create a user account on the 4th boot, but still haven't installed anything extra on it.
It's also really slow to boot. A few minutes in stage 1 before it asks me for the decryption password and then another few minutes to get to the login prompt.
All of this is without any graphical environment. I was planning to go with a low resource desktop like xfce or cinnamon (are they still maintained?), but any tips on what to look at before I possibly introduce more instability?