Just what I needed to make me switch from Chrome. Works fine on M1 Mac but setup instructions work fine, as long as you read them carefully. I missed needing to link the brew-installed code to Firefox. Once I did that, everything worked great. My requests for enhancements are small: the ability to color the menu bar based on selected profile and the ability for user-uploaded profile icons.

Overall this is just a great addition to Firefox, which I haven't used in decades but am thinking of returning to because Chrome has become so, how to say it, greedy.

Thanks, @nulldev. Really appreciate the effort.