Sorry jeps for posting wrong info, my mistake.
Strange, when I tested on ubuntu 21.10 yesterday, then could reproduce with 'sudo pip install twisted==18.9.0', but not with 'twisted==19.2.0', and stopped testing afterwards. However now when thinking about it, then never gotten your posted error either, only the failed auth one previously posted, but could reproduce issue of not could add torrent however.
Anyway, just regarding some previous questions, then in my testings, then the apt installed stuff, took precedense over the pip system-wide installed, it's also using /usr/local for system-wide pip installs, atleast on some distros, don't remember if on ubuntu, sorry, think read once it deferred based on distro selected default.
It's easy to change twisted versions using pip, and you don't need install system-wide, I never do personally for myself, but just post like that because guess most want that, and is easier often for reasons not needing go into here.
So need to uninstall python3-twisted, think it's actually called python3-twisted-bin, from apt, and then can install and use the one from pip(just called 'twisted' there), which should be latest ver when not specifying ver(==) specifically.
Yeah the deluge-develop PPA currently features libtorrent 1.1.12, so if using old distro, then will "force" that, though ubuntu LTS features 1.1.13, so will override that PPA, though still not valid for dev-deluge, but can add the libtorrent 1.2 daily PPA Cas previously posted, or use the one from pip.
The easiest is probably to rely on pypi for everything i.e. if having git installed, then install latest deluge-dev, twisted and libtorrent by running 'sudo pip install git+
https://github.com/deluge-torrent/deluge'(if not going through git and instead pip install https-url, zip or folder, then need manually add RELEASE-VERSION first, as bug about that e.g. in my posted zips I added that manually to overcome), 'sudo pip install libtorrent', wih firstly uninstalling all deluge components gotten from apt or PPA, and if not already removed with deluge, also libtorrent-rasterbar(probably have 9 and/or 10 after name) and python3-libtorrent and python3-twisted, run uninstall command for all those(through apt) just in case. Otherwise maybe can install twisted from pip, and then afterwards deluge and libtorrent from PPAs, though don't know if accepts that or installs own ver, hence my thought to just use pip for all, but your call of-course(I don't think you can uninstall twisted after installing deluge, from apt, unless adding dep-overridding switches to apt, I mean to install from pip afterwards).