I'm logged in to github site on my phone. On this forum when I choose to login or sign up with github it redirects me immediately to the forum, and the forum doesn't see me logged in.
When I created this throwawa account using email I've also seen BAD CSRF error.
I've got cookies enabled in Safari and I've tested with content blockers disabled. Still, seems like some cookies or csrf tokens aren't working here in Safari/iOS. Can you check it?