I use Brave on mobile and iPad and have not had an issue with it being unsupported.
It’s odd to be sure, and I guess you have no idea if anything changed between yesterday and today? Do you use a vpn, or had privacy settings in brave which might have prevented it from running certain scripts or loading content? It may have been trying to block things server side which would throw an error.
Good that it’s working now, but always nice to know why something didn’t work.