Programming and reading.
555 is still in beta, so I wouldn’t be surprised if something doesn’t work. That said, I haven’t experienced what you have (on GTX 1070 TI), though using 555 causes lots of kernel errors for me. Checking dmeg might reveal something in your case as well.
You can set the initial value directly in /etc/environment, did you check that? It could also be set only for your user, so it might be in ~/.profile, ~/.bashrc or ~/.bash_profile` (or the rc file for your shell if you’re not using the default bash).
Edit: I suppose you could also have added a startup script in /etc/init/ or /etc/init.d/, or in /etc/rc.local
Immutable distros aren’t immutable in the home folder though, they would be unusable otherwise, so that doesn’t solve OPs problem of dotfiles/personal files (I know nixOS tries to get rid of dotfiles, but in my experience that almost never works, it’s only helpful for replacing config files in /etc)