Hi Patrick and David, I seem to recall that my bug was initially limited to only the .mkv format.
But, now all renders fail. Even kdenlive projects that used to render to .webm fail. Maybe this bug is related to #847700. In it, David wrote Tested with WebM, MP4, MP4-H265, Webm... The render doesn't end. I just tried mv-ing ~/.config ~/.local and ~/.cache and re-rendering a kdenlive project to .webm that used to work. No luck. It still crashed. Comments welcome. So, Kingsley -- Time is the fire in which we all burn.