What is the most difficult problem that you have fixed in linux?

I had problems with the session manager My lightdm was broken and I tried to fix it. Disable, enable, start, stop the service in systemctl I have changed the configuration of lightdm I've tried different lightdm greeters But the problem wasn't with lightdm, it was xorg. I don't use xorg, and now I use terminal session manager "ly" It will work even without xorg