Same here, was about to reinstall everything so thank you all for saving me the trouble!

you should ask this on github, that no-name developer who created steam integration plugin. gog does not work on integrations besides xbox so they can't fix anything in external code. go to github and create bug report for plugin, it won't help asking on gog forums
https://github.com/FriendsOfGalaxy/galaxy-integration-steam

Didn't they do steam themselves?

no, only xbox, every other integration is on no-name people from github. galaxy 2.0 TOS tells gog are not responsible for 3rd party plugins as well.

Though we really don't know if it's not handled by some workers of GoG in silence and throw it out as a community Plugin to be save versus Steam Policy & Stuff.

But yeah, it seems that Steam-Plugin is f**** for now, when i disable it GoG Galaxy 2 runs properly, but when i enable steam plugin i've way to many different errors. From Metadata loading ad infinitum, up to crashes / freezes and stuff.

create ticket on github, with your plugin logs. that's the only way to address this issue atm

Some other guy from Romania figured out a work-a-around in a random thread (I can't find his original post now, they might have deleted the thread) - anyways, as soon as you open GOG Galaxy, immediately switch to the store page and wait a bit, the library will load correctly and if you are really lucky, your friend list might even show up.

Looks like we're back to normal, all Steam games came back for me.

Thanks a bunch to whoever fixed this - Life is good again!