About the same number of people as use Firefox according to this site: https://gs.statcounter.com/ Which is the source used by caniuse.com: https://caniuse.com/usage-table

Yeah probably 3 people

In all seriousness, yes, unfortunately, I know at least one person who daily-drives the Samsung browser. Why, I can't imagine. I mean, even Chrome is better than Samsung Internet, and that's saying a lot, since Chrome is essentially Google spyware IMO.

I found that it's only useful to browse sites that don't have dark mode (built-in conversion without any extensions) since they actually put some effort into making it work.

I tried it for a while. It's a pretty good browser which at the time had features others didn't. (I want to say extensions but I don't remember). In the end I am never comfortable using a closed source browser so I switched to Firefox.