I got a new Mac so I'm trying Safari again (surprise surprise, it seems to be significantly more performant on an M-chip than an i9... I suspect there's not been a lot of focus on x64 perf tuning of late!)

I realise insular decisions is a very Apple thing, but jfc, its unwillingness to map mouse3 to "back", even as an option, is baffling. Every other desktop browser has done that for zillion years because it's a very sensible mapping. We don't all use Magic Trackpads.