Okay, so it's not just me.

Yea... It isn't listed as anything for me, GOG Connect page is just blank, it isn't under "unavailable" either. And yeah, if it doesn't port the DLCs over - ...This action is pretty much pointless anyway. :( Shame. I was really hoping to migrate as much of my library as I could to GOG, as I'm buying new games here as well if they're available.

This is NOT a tragedy, but unpleasant. I have the complete collection of Stellaris in Steam. But Gog Connect for only base game doesn't work for me.

I've writtent to the tech support and got automatic message that Stellaris has been deleted from GOG Connect because of technical issues with library checking. They hope to solve it and make this offer back in the nearest future.
Ok... I think they must make it back with possibility to transfer DLC too... Otherwise it won't be worth the efforts...

For the base game only without DLCs its not worth the effort. Cause no one will purchase dlcs one time more on GOG and no one will play Stellaris without the bought dlcs.

I agree. Though it looks like there is no public method for getting list of DLCs, so that may be why. They simply can't check which DLCs the user owns alongside the base game.
Although they could probably check for unlocked achievements associated with DLCs as a way to check whether the user had played with them. But it isn't reliable in anyway so...

Paradox themselves are weird with DLC ownership. Their own launcher displays a different set from their website (the former shows at least most DLC acquired through Steam, the latter doesn't, I haven't tried actually installing or running anything through their launcher since that attempts to run a .bat file with admin privileges), which in turn has nothing to do with your Steam library, and now GOG enters that mess. All the while, the Steam account's connected to the Paradox account.

I don't expect GOG to get any meaningful information out of that mess.

Anyway, it's only base game without DLC's, but I hope Stellaris returns to connect. Maybe even with DLC. Without DLC really does not make much sense - they make up a significant part of the cost of the game.

I'm giving up on GOG connect in terms of Stellaris here.
I'm just getting the rest of it on Steam. :-(