I was told that Orion has a similar UI to Safari but allows installation of Firefox plugins. I switched from Firefox to Safari because I can't do without tab groups.
Firstly, I had the unpleasant experience of importing my 40 Safari tab groups into Orion, which implements tab groups as separate windows. This nearly crashed my system.
There seems to have been a discussion about this already here, but the developer has prevented further commenting, because I guess he does not want to hear any more from the many users who don't like the poorly thought out UX decision to ditch tab groups for some kind of window history scheme: https://orionfeedback.org/d/468-tab-groups/21
Many users have explained at length in the above thread why they prefer tab groups in Safari. They have ben ignored.
I just wanted to say that there is no way I am going to use Orion at present. The few extensions I miss from Firefox do not compare to the massive workflow boost provided by tab groups.
Tab groups allow me to organize my work all in a single window, including moving tabs between groups. Safari's UX is a far superior method of managing my research workflow. Tab groups also do not bring my system to a near crashing halt as happened when all my tab groups, imported from Safari, opened in separate windows in Orion.
I am also not very impressed with developers who have such low regard for feedback they receive from users. I'm not going to put trust in software designed under such an ethos.