I realize that the conversation has been continuing outside the bug tracker.
9d25ee30b188f9202cc14f7cd25ba8a1c3ec1a72 has a working version of Calibre 5.21.0. 6dffced09ecda024e0884e352778c221ad066fd6 is the commit where it broke. That's a big merge commit, and Calibre is only broken in one of the parents. I started to do a bisect between the bad parent and the commit which bumped Calibre's version, but it contains merges and --first-parent seems to be less useful there than in the earlier bisect session. I see a recent update to Calibre 5.36.0, but I'm taking a pause because waiting for QtWebKit to build is annoying. That is the summary of what I know now; I'm also happy to copy the rest of the emails back into this thread, with Leo's permission. Jacob.
