Unity 2017/2018 - Open Project screen is grey. Can't select a project.

Hello, I haven't been able to launch the Unity Editor for the last few days.
I've been using Unity 2017.3 for a while now and 2 days ago, after restarting Unity, the open project screen took forever to show, but it stays grey and I can't see/select any of my projects.
I updated to Unity 2017.4 (and also tried Unity 2018.1 later), but the problem persisted.

Someone said I had to change some things and extract a zip in Appdata/Unity, which I did, but that also didn't work.
Now I've uninstalled every version of Unity and erased every trace of it from Appdata and every other place I could think of to make sure a clean install would be 100% clean, but after reinstalling 2017.4, it still doesn't work. Forcing it to go into offline mode by unplugging the LAN cable also doesn't work.

TL;DR:
Unity takes forever to startup and when it does, I get stuck at the 'Open Project' screen which is completely grey. Can't see my projects or select anything. I removed every trace of Unity and did a clean install; didn't solve it. Forcing it to offline mode also doesn't work. Screen will stay grey.

 

Have you tried launching unity while all network connections are disconnected? (to force offline mode)

 

I had this grey screen issue once before a few months and turning off all network connections did force it into offline mode and it was fixed after that, but that's not the case this time around.
Turning off my connections and unplugging my PC still results into the grey screen.