Just saw that the Feature versions tab in Studio has new version entries for "Base Theme" and "Support Theme" (the latter probably only exists if your community has worked with Khoros Professional Services to implement this). Our community is currently on version 1.1 for both of these features while a newer 1.2 is available. Unfortunately the article About feature versions doesn't cover these yet.
Can Khoros share more information if it's worth changing feature versions and what would change?
@Claudius - were you ever able to find information on this? I was attempting to update the base and support themes before starting regression testing for 20.1, and I ran into the issue described here: Requires dependency to upgrade Base Theme skin
So I still don't know what these features entail. 😬
Count me as an interested party in finding out about these as well.