So basically once unlocked they all showed up on the GOG Galaxy activity summary but if you look in the "My Progress" tab or directly on your gog.com profile they're still greyed out.

So far I have encounter five of them:

Dual Wielder - As the Warrior, kill an enemy with two weapons.

No Context - Win the game within the first 10 rounds.

Row Your Boat - Use a Raft to cross the river.

Powerful - As the Wizard, raise your total Craft to 10.

My First Runestone! - Unlock your first Runestone.
(This one pop-up everytime I choose my runestones at the start of a new game)

This one is especially annoying since I get it after each finished game - I already have it more than 10 times and it messes the game's achievement percentages as well as GOG's achievement totals, both monthly and overall.

Can someone at GOG please pass the list of bugged achievements to Nomad Games for fixing?

+1 : I got this one two days ago and it keeps popping every time I open a game, wich is annoying and pollutes the achievement page. I am surprised Nomad Games has still not been able (or not even tried ?) to fix this old bug.