I used the paradox launcher V2 for linux to play the game and as it did not update with the latest patch (after trying everything else) I contacted support and got the answer that:

- pdx launcher does will not support newer versions of Stellaris
- it was a mistake that it worked with the keys from GoG in the first place

being specially a problem for those who bought some parts of the game from GoG as you won't be able to play the full game beyond 3.4.5 via the pdx launcher any more
and for those who used the launcher on linux because there is none from GoG

PS: posting this here because I came across postings on different platforms with problems related to this

I'm not sure if you are aware, but you do not need to use the launcher to play the game. In fact, I would recommend against it as it is needless bloat. Just run the stellaris executable in the game folder. You can manually update your shortcuts to point to that as well.

To update the game, just download it again from gog and install it right over the top of the old install. Just choose always replace when it finds duplicate files.

If you need any help with this, I can give you more through instructions.

I know that it works without the launcher

The point is, it was never intended to work with the launcher in the first place and is considered a bug by paradox

So I post this for those who still use it and run into problems (and the paradox website still say it works) and older forum posts suggest using it