They aren't missing, but bundled together in https://www.gog.com/game/xcom_2_reinforcement_pack
I got another question while at it - is there a way to add mods, like on Steam workshop?
I'm pretty sure there's lots of mods for it on Nexus.
Oh yes, there are plenty on Nexus. XCOM 2 is also one of the games officially supported by Nexus' Vortex Downloader.
why not have the "collection"?
steampowered .c om/bundle/7118/XCOM_2_Collection/
even then there would be missing dlc, but still easier to get that and then the remaining stuff..
i'll wait for steam parity. if it ain't coming, so be it..
and if the game is now "finished", just have a "complete pack" even if created by gog. so just add all xcom2 content into a gog buyable single purchase and then wake me...
i won't buy bits and pieces in 2020 like this for a game this big...
the way dlc is shown/handled on gog is horrendous. copy the steam method verbatim. have store page show any/all dlc under main game not to side like now. not only that the side nonsense only shows 4/5 if game has more..
I checked all available DLC on Steam's XCOM 2 page and compared it to the GOG DLCs. There is no difference.