Yes the servers have mods even with non modded servers I get the same issues. I've updated my drivers, turned off overlays, load in window mode and verify game files. but not seems to work.
#Never ending black screen when joining servers
midnight tendon
midnight tendon
wispy valve
Can you try doing a full reinstall?
First, uninstall the game, then go to "Steam\steamapps\common\ProjectZomboid" and make sure there are no leftover files or folders there.
After that, go to “%UserProfile%\Zomboid” and delete everything there except the “Saves” folder.
Then just install the game again and see if that helps.