Sp00kie, there are some errors in log, like you showed, for the initialization for the gtk part i.e that part should be gtk3ui, but other issues too, when I previously spent a little time seeing if I could fix the gtk part, but I believe can be ignored as the daemon does have it initialized you also can see from log and when shutting down the log states the plugin shuts down too for daemon part, I believe remember it listed in my log when testing it. I can't help you with your issue, unfortunetly, but several months ago, a ticket was made on github stating that deletion only worked when opening the webui and into preferences selecting apply and ok. Springjools posted a link to a deluge ticket stating deluge not deleting torrents whenever the webui wasent open, and didn't mention autoremoveplus, but I don't know if was related. I'm not in front of computer now, so cannot test this myself. I'd suggest making ticket about it on springjools github, or repost in the old ticker I referred to above, it's called something with not deleting or removing in title and 3 or 4 months old.
(Edit: Sorry was an old very long ticket on the original authors github, started long ago, and where springjools announced his fork and got reported said issue around 6 months ago and responded the above mentioned, so make new ticket on springjools github I'd suggest. Old ticket where mentioned a few times in, here: https://github.com/omaralvarez/deluge-a ... /issues/50
Psycholyzern, so you're on deluge2 and having installed python3-requests, and not seeing a preferences menu for autoremoveplus in the preferences menu of webui? If so, then sorry I don't know issue if you're on springjools latest release linked previously. I'd suggest running with debug-logging and examine/post for further troubleshooting.
Edit2: You mentioned wrong path, you do have it under plugins folder right, under your mentioned path, but you should have, as else couldn't see it and enable it, as wouldn't show. Use manual install as just stated, and don't select to install it, only enable it, to exclude all other issues, as have read about such failing before. If you start deluge from e.g systemd or whatever, then keep in mind it often starts deluge daemons under a deluge user, so should have plugin under that config dir and not your regular account.
It was suggested to restart webui daemon and page too for your issue I just read and was stated to work.