I think it is unlikely the dev will add it to GOG. Below is a quote from the dev on his previous game (TTL), some of which would probably still apply for this game:

Originally posted by Sinister Design:

That's not currently planned. TTL takes advantage of various important Steam features that I don't believe GOG offers an alternative to (e.g. in-game browsing, uploading, and downloading of player-made campaigns; online multiplayer; etc).

Plus, GOG is just kind of annoying to deal with when it comes to getting paid--you have to manually fill out an invoice in Excel and email it to them every few months. Add to that the fact that their market share is quite small and it just doesn't seem super worth it. I'd consider it if there were a lot of demonstrated player demand, though.

Personally, I normally prefer GOG over Steam, but I get these concerns.

Got it thanks 🙏

I would immediately buy the game on GoG, if it was available there at launch.
Any update on that?

I don't know if it's supposed to be the same game or not, the graphics are the same I think(?)

It's called "Telepath Tactics Liberated" on GoG.

Edit: Same dev, different game.

Yep, the dev did eventually release the game I mentioned (Telepath Tactics Liberated) on GOG after I quoted his post! So I am not sure on the dev's current feeling about releasing Together in Battle on GOG.

Originally posted by Loz ~:

I don't know if it's supposed to be the same game or not, the graphics are the same I think(?)

It's called "Telepath Tactics Liberated" on GoG.

Edit: Same dev, different game.

Its different game, same Devs, but with the same engine and some similar mechanichs. If you enjoy togheter in batlle you will enjoy Telepath Tactics Liberated. Its really a good tactics game.

Im hyped for the release, just 5 days hibernating till 6 May