I'm seeing the same, applying the patch from [1] works around the findCaller error, but then I run into [2].
Downgrading libtorrent-rasterbar10 and python3-libtorrent to version 1.2.5-1.2 makes everything work again, although it's a bit inconvenient because that also requires downgrading to Python 3.8. Not sure if the problem is with Python 3.9, and/or libtorrent 1.2.9. [1] https://git.deluge-torrent.org/deluge/commit/?h=develop&id=351664ec071daa04161577c6a1c949ed0f2c3206 [2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=977143
