@baris strangely enough, the category list loads now! And it doesn't look like there's any circularness in the list.
Still, trying to manage the admin group via /admin/manage/groups/administrators or /admin/manage/admins-mods results in a gateway timeout. I've also enabled verbose logging, which displays this upon visiting either of these two urls:x.x.x.x - - [01/Nov/2022:17:12:10 +0000] "GET /forum/admin/manage/admins-mods HTTP/1.1" - - "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106.0"
Now there's no response code. Strange.