Offline games still work fine, but that's sadly not interesting. It does show that it's not the game files being at fault here.
This is new since last night, after a "You've been disconnected from the server" error (I was the party leader). Now as soon as I join or create an online game, instead of loading into town I hear everything there and can move/dash but screen is completely black and the only way back is to figure out where the Settings icon is and then guess/find the "Return to Main Menu" option is and blindy click that. Some people say they had success using VPN and I've tried with every EU country I could think off and no change.

And I appear offline to others looking at the friends list. Even tho I can msg them. Dunno if this is related.

I also cannot alt+tab out anymore at all. Hence the need for the guessing game mentioned above where to click to be able to go back to main menu.

EDIT: I managed to get online on the friendslist but still the same, whether I'm the party leader or not. I simply cannot get past the black screen when starting an online game. What I did notice though is that my friend told me that I do not move or dash at all, when I was thinking I was due to me hearing the sound of it when clicking/dashing. I'm simply immobile to them so I clearly haven't fully spawned in at all. Then we get disconnected both after a little while. In either case, all black screen.

EDIT2: If I use a completely fresh character I can join a friend's game, so it's clearly something that has gone wrong with my other character.
EDIT3: Once. It worked once. Then same thing on that character.

This REALLY needs to be looked at. Seems to be quite a few judging from the forums and the discord.

EDIT4: Found a solution that works for others.
1) Create a lvl1 toon.
2) Enter Stormfall and cancel all Dark Market activities.
3) Leave and enter with your normal toon.

My problem here is I can't even get in with a level 1 toon, but for others in the same boat this may serve to help them. I my case there's something else going as well. I only show up on friendlist for a brief second, and most of the time invites sent to me doesn't show up on my end. Or in the few cases where it does show up, and I accept, everyone in the party gets disconnected when I try to join the game. So there's some real server issues with my account, maybe connected to steam in some way.