It’s mobile where I like the tab groups really, and unfortunately the extensions I’ve found that try to mimic the functionality don’t work there. Honestly that’s the big one but it’s pretty major for me. With the way I tend to browse and research topics it’s hard to manage without tab groups.

The only other big one is services that don’t support Firefox. I use GeForce Now for game streaming so I do that through Brave.

Fair, unfortunately though the chromium browsers have features that I enjoy that are not available in Firefox on mobile (for example, tab groups).

Brave and Vivaldi are chromium based but have adblocking built in rather than relying on an extension. So while they will eventually be impacted on extension support, the built in adblocking (which is quite robust) won’t be affected.