git bisect
narrows it down to this commit which migrated the deck configuration to protobuf. I’ll take a look to see where the bug is. This means this bug affects Anki 2.1.28 and later. My reproducing test case is basically just:
% rm -rf ~/.local/share/Anki{,2}
% make run
And then check what the starting ease factor for the default option group is. This means the schema isn’t being converted or anything, it’s a completely fresh collection and deck.