with chromium/ungoogled chromium/maybe other derivatives, you can put multiple browser profiles to ~/.config/chromium and add --profile-directory="xxx" to exec path
Braver user here: I can add multiple profiles through the GUI - which I use to separate my Google usage from my general internet usage. Is this not supported by base Chromimum?
I might have missed it, but I don't think it was back when I was looking for equivalent of Firefox's `-p` command line arg a few years ago. I did however end up setting up a dedicated launcher for every Firefox profile as well instead of using `-p`