As mentioned, the downgrade works, but apparently 2.1 has an ending slide bug, causing it to be stuck at one slide. Apparently it's a bug connected with BoW DLC (https://forums.obsidian.net/topic/105175-stuck-on-epilogue-page-cant-continue/). It happened to me at the same page as described in the linked topic.
The 2.1 version also shows I have BoW installed at the main menu (when I really don't), so could that be the reason for the ending slide bug and the "missing dlc" bug in 3.0?