I own both Northgards: Steam and GOG. One is for me, one for my GF. Now i'm trying to go online in GOG multiplayer and see no games in list.
Also I noted that versions are mismatching: 2.4.19.20720 in STEAM and 2.4.16.20634 in GOG.
Are you kidding me?
UPD: Tried to reinstall GOG client - still old version and dead multiplayer tab.

The same WTF is going on

There is a reason for this and it will be fixed in the next few days. The latest update broke Solo mode on GOG and made Galaxy mandatory. One of the blues explained it on another thread: https://www.gog.com/forum/general/drm_on_gog_list_of_singleplayer_games_with_drm/post448

this must be a Joke!
for like a week i cant play the game with friends just because i got it as a gift on fucking GOG!
For real...as it is not enough that i need 4 different platforms to play my games now they even have several version of the games so i cant play with friends. So u want me to buy the game a second time on steam?
Dunno if i should laugh or cry...u should give all GOG players of Northgard the DLC for free as compensation

Well I already asked them to transfer my gog license to steam. I'm tired of discussing / reading about such issues.
Singleplayer was nice to get started / playing the campaign once,
but the only thing that kept me was playing online with a friend (who bought it on steam).

Since they refused to transfer my key and there is no way that I will reward them with paying for the steam license too,
I just looked online. I'm not sure that links are allowed here, but there are online key sellers which offer northgard on steam for 10€. It's a shame that we have to buy it twice in order to play it freely, but it's probably the by far most simple solution.

19/03 update of GoG v2.4.16.20634

22/03 update v2.4.17.20663

23/03/2021
Update version v2.4.17.20672

26/03/2021
Update version v2.4.19.20720

01/4 (today) crossplay/multi still not playable. Great work ! Ithink they dont care tbh

19/12
Still no 3.0.5, so no more crossplay with Steam version for now.