With one of the recent updates the devs implemented both Galaxy and Ingame achioevements. Unfortunately both are not working and the devs so far were unable to fix those. Fixing Galaxy achievements so far is not possible for the community as well so we'll have to wait for the devs to find a fix. However at least the ingame achievements (which don't show the achievement descriptions) are fixable.

https://www.gog.com/forum/general/list_with_gog_games_that_have_ingame_achievements_v2/post137

After investigating, there is a simple fix for the broken achievements. I took the SteamWrapper.exe from The Gateway Trilogy, and used it to replace the one in The Dream Machine game folder, and I also added some information to the SteamWrapper.ini file that was missing, so that it look should look like the following: You can download the two files below, extract and replace the ones in your installation directory, and they should work. I did a 100% run and all achievements unlocked in Galaxy.
https://www.mediafire.com/file/tpz5qcfk77xhnex/The_Dream_Machine.zip/file