Steam seems to be now fixed, but ...

* Battle.net requires you to log in every time you reboot.
* Ubisoft Connect just doesn't work.
* EA just doesn't work.

Once upon a time, this was a good launcher, but it's been neglected and the integrations just haven't been maintained. Surely there must be some working integrations out there.,

Steam intergaration to Gog is still busted
* yes battlenet loves a login
Ubisoft doesn't work = correct
and EA has never actually worked because their server was setup incorrect [thats Origon server], you can get EA games to sync with Gog if you understand the limits of their networks

1 open EA app and sign in... make sure the game library shows your games and opens a game... if it doesn't then their server handshake has failed and that has nothing to do with Gog
workaround for Windows users is to restart your computer and try signing back into EA app... it may take more than one restart but once their server wakes up you can then open Galaxy and add your EA game as a 3rd party option... link to the EA app exe and Galaxy will track your time [other badges sync once the app updates]

For ea try this: https://twitter.com/p0358/status/1635796691902160896

For Ubisoft Connect try this:
https://www.gog.com/forum/general_beta_gog_galaxy_2.0/ubisoft_connect_integration_not_remembering_my_account_details

So far both work for me, don't know how to do battle.net though.

All integrations working fine here, even the Steam one with the latest fix.

EA (Origin plugin) can find the games I own, but can't detect the installed ones, also I can't install them from galaxy.

The only way I found to launch them from Galaxy is to install them directly from EA client and then add them to Galaxy as "Others" that I own.