Lack of this feature kept me from switching (from FF to Brave) as well, for a long time, maybe a year.
But a few months or so ago I decided to bite the bullet and just try living without it and see how it went. Haven’t looked back.
In retrospect, I feel like the automated Brave privacy protections already fulfill 90% of what I’d get from Containers, without the overhead of managing them. I could be wrong.
I do have a few separate profiles still though, but this is because in Brave I can install different extension sets into different profiles; whereas with Firefox it was all-or-nothing, unless I wanted to create a new profile in FF as well, and then you’re back to square 1 again.
So I have a Shopping profile where I can install Honey and a few others that I don’t want reading all my history from my ‘Main’ or Default profile. In some ways this is actually better than FF + Containers.
All that aside, one thing I do miss about this arrangement is having all the bookmarks, history, etc. in the same instance/profile. And I don’t feel like setting up Sync multiple times for these profiles, it would be nice to just do it once and have everything there. So I’m considering the idea of syncing all the profiles together onto a single Sync Chain, but shutting off the Apps and Extensions sync. In theory it should work to get the bookmarks, history, etc. all in the same place.
Doesn’t solve the problem of automatically opening a given site in the ‘right’ profile but small price to pay for all the benefits. YMMV though.