SDDM new version 0.19 was released in dec. 2020. Link to changelog : github.com/sddm/sddm/releases/tag/v0.19.0
There's a long-standing open WIP PR to bump to a >0.19 snapshot. I think the release ended up being buggy and they haven't made a new release fixing the issues since.
That version is just broken, and no suitable snapshot has been produced yet. *** This bug has been marked as a duplicate of bug 790713 ***