Yes, tried that and it was still the same.
I figured out this is not related to mods, because I am running game fine with mods.
For example now I was having issues connecting and I disabled WindowedLobby and it helped to get game started, also before disabling WindowedLobby helped to get games started more times than with WindowedLobby but still randomly I get either grey screen or I am stuck at connecting, even after disabling ipv6, I was stuck in loading screen.

Funny thing is that I just created another game with exactly the same game.prefs file and It works fine... at this point it's a roulette
game_26794810.log

I started the game, but for some time I struggled to get it working because of the grey screen issue.

I began testing various changes in the game.prefs file, as it seemed to be the root cause of the problem. I remembered that I had changed the primary_adapter setting from '1920,1080,60' to '1024,768,60', because I noticed that this was the default value in a working game.prefs file.

After that, I restored my backed-up game.prefs file with this slight modification. The game would sometimes load correctly, but other times it would get stuck on the grey screen.

At one point, I forgot to quit the game, and it remained running in the background (windowed grey screen) while people joined the lobby. When I maximized the game, it looked very strange—I took a screenshot because the visuals were completely broken.

From what I saw in the log file, the host suddenly tried to load all textures at once and failed.

I’m also uploading my game.prefs file. Hopefully, this will help identify why the game behaves this way and which specific setting needs to be changed to fix the issue.

game_26794611.log
Game.prefs.txt

@Sheikah said:

Delete the client installation directory and reinstall

thank you ! It worked but uninstalling didn't do it, i had to delete all data files.

It was short lived because first game launched, second one had a grey screen, i found another thread and they recommended to delete game.prefs file , I did and it worked, just then it was pain to copy all the important settings back.

Noone can connect to me while I am hosting the game, I host custom game and multiple people try to connect and they fail, when looking at the FAF ICE adapter I observed that for whoever tries to connect the status is changing from checking, disconnected, gathering, awaitingCandidates... and all over again, I changed to allow IPv6 in settings, it didn't work, then from aeolus chat I got to know that Germany 1 prefered coturn server might be bugged..

Changing coturn to Finland helped because someone finally connected.. so is that the case now with Germany 1 server ?

Are you still working on the mod? rn i use it only for factory templates and build templates will be very useful