I’m using Brave for the same reason - compartmentalisation via profiles (“People”). Keep LinkedIn and other data vacuums quarantined, thank you very much.
You should check out containers for Firefox. It does the same thing without having to open multiple windows / instances.
And I find Firefox to be between Safari and Chrome in efficiency. Especially on an M1 Firefox seems to not drain the battery like Chrome.
For “dirty” sites like LinkedIn I simply open a new private window in Safari.
Multiple profiles is the reason I have a chrome based browser on my machine at all.
I'll admit it. it's Microsoft Edge. big reason is compatibility with some other Microsoft stuff I use at work.
otherwise safari is the daily driver.
It seems like such an easy feature to add, but I'd bet there are Apple politics in play preventing Safari from adding this feature.