Firefox has a profile manager (the thing that’s also exposed to about:profiles). Run it like firefox -profilemanager and you’ll get a profile switcher.
Run firefox -profilemanager -no-remote if you want to open multiple different profiles at once (only the original one without “no-remote” will open new tabs when you click on links outside the browser). You’ll probably want to make a shortcut for different profiles though, not sure from memory what it is (but probably -profile ProfileName) and then you can easily use profiles.
The support is actually pretty decent, just kinda hidden. You don’t get a profile switcher because the browsers are completely separate, they don’t really know about each other.