I just reinstalled NixOS 21.11 on a couple systems. I think this permission problem is new. (I’m not sure because my old system is suddenly very dead.) It feels like some config file isn’t getting written to, but ~/.config/BraveSoftware/ seems to have permissions 700 all the way down.
This feels similar to a Konsole issue I had but that turned out to be solved upon restarting the system; this issue, though, hasn’t succumbed to that strategy.