[2020] Crashing upon game initiation, can't even load up main menu

There are a couple of workaround for Citrix Workspace that might help so you can have both installed. :)

https://forum.paradoxplaza.com/forum/threads/citrix-workspace-crashing-cities-skylines.1158220/

But yeah, Unity games think Citrix is the graphics card, which it isn't, so the games crash.

If you don't need Citrix, then removing it is the simplest option. But if you do need it, check out the workarounds so you don't have to uninstall Citrix whenever you want to play. :)