I always seem to end up with duplicate profiles, or `about:profiles` refuses to open ("Another copy of Firefox has made changes to profiles.") and on and on with various hiccups and speedbumps. Small annoyances, but profiles on Chrome always Just Work, and the half-dozen times I tried it on FF was always death by a thousand cuts.

It's been a few years, so I'll give profiles another try I guess. Containers likely won't do it since multiple profiles all use the same domain (console.aws.amazon.com being the obvious one).