I’ve tried both of those, tree style tabs kinda works, but isn’t ideal. It’s also not an option on mobile at all, and I prefer to use the same browser for mobile and desktop for tab sync/etc.
I used Firefox on desktop and mobile for a few months this past year, but never got as nice of a work flow going as I had with Brave. Then a Firefox update for mobile broke the browser for a week or two (crashed on launch, resetting app data/reinstalling didn’t help) and I went back to Brave, and realized how much I missed tab grouping and some other stuff.
I’m keeping Firefox installed, and I’d be happy to switch back someday if tab grouping gets ported over.