Both games have invisible achievements in development mode and they can be made to work. Please refer to the broken achievements thread, section BROKEN ACHIEVEMENT FIXES in the OP for further information about this.

For Legends of Eisenwald, a roll back to version 1.2 is required. Note that the overlay doesn't work, so there are no achievement notifications. The achievement 'Cursed Jack' is also missing from GOG. Following the discussion in this thread, some achievements may not work. I haven't tested the game extensively, but anything that should get unlocked worked fine for me when I played.

For Eisenwald: Blood of November, a patch is required to make them work - without it, the game tries to unlock achievements from the first game. The direct link to grab it is here. It includes a readme that tells you how to install it.