Tab groups also exist in chrome, brave and edge (was behind a flag last time I checked), and presumably other chromium-based browsers too
I especially like the auto group feature. I start a search and every link I open in a new tab is added to the group (which is collapsible).
I do a lot of spec digging doe my work. It’s not uncommon to have 3 or 4 tabs per data type with many data types.
Plus, there's the usual stuff of password management, email aliases (nice for not giving out your email), and private relay, which is basically TOR lite for grandma. And what about ad blocking?
Was it added to the core browser?