Never used command line for profiles, I'd just go type "about:profiles" > "Launch profile in new browser". This opens a new window with that profile, but you c

Never used command line for profiles, I'd just go type "about:profiles" > "Launch profile in new browser". This opens a new window with that profile, but you can switch between each window at will. The lack of discoverability of that "about:profiles" page is indeed a UX issue compared to chrome, but other that that it works pretty well. For most use cases, I find the more lightweight multi-account-containers more useful though.