I’m only half joking when I say that managing separate accounts for various parts of HTB is what finally pushed me over the edge to using a password manager. The good news is I can confirm SSO is planned. The bad news I don’t have an ETA for when it will be released. The concept was first brought up when Academy was released.
The forum is currently using Discourse and 2FA is available for setup under, Profile → Preferences → Security → Two-Factor Authentication.