Ok, telling people to open a command line and TYPE firefox -P is HARD. In chrome you just click the icon in the upper right and select whatever profile you want.
It makes no sense that you have to either open about:profiles then select "launch in new window" or open the command line to start a new profile, makes NO sense at all.
You can open a firefox private window with a keyboard shortcut, but if you want to be logged into two different accounts in two different profiles, you have to go through a minimum of three non-intuitive steps.
Even the extension that adds the profile switching doesn't work anymore because it's not maintained.