This is the one feature that has kept me from switching to Firefox Mobile. Tab management and tab switching is harder on a small phone screen than on a desktop, so well-designed tab features are essential. Firefox on mobile feels clunky and awkward to anyone who is used to tab groups in Chrome.
All I'm gonna say is Firefox Mobile still isn't up to par compared to Firefox on PC.
Firefox on PC is great. I want to go all in on the Firefox ecosystem, but missing features in the other Firefox apps, aside from PC, are a huge dealbreaker.
Firefox Mobile lacking a simple but useful feature like tab grouping really solidifies that.