After installing ai_war_2_2_800_46339.sh I get the following error:

Running AI War 2
./AIWar2Linux.x86_64: error while loading shared libraries: UnityPlayer.so: cannot open shared object file: No such file or directory

And it doesn't matter if it's a clean installation or over 2.715.

Confirmed. Doesn't work for me either, displays the same error message. The library UnityPlayer.so is indeed missing.

Discord crowd said that it's fixed in 2.802, but it's not available here for some reason.

I had the same issue here on Ubuntu....
Well, if they've fixed it apparently there's not much we can do except wait for GOG to make the new installer available to us?
It's really a pain in the *** not to be able to have the opportunity of using Galaxy on Linux. I don't exactly mind downloading installers manually for a game, but when it's an ongoing development project such as this one, having to redownload and reinstall everything every time there's a small patch becomes a real chore...

Can someone report it to GOG? Since I'm not on Ubuntu, I'm afraid that they can just sweep it under the rug and do nothing. And I'm not sure that Arcen games are getting the messages.

Build 2.803 is online and working for me.
Hooray!