There are two routes in – tech-artists.org and discourse.techart.online. The HTTPS config for the techart.online domain is broken right now, I haven’t had the chance to poke at it but it’s probably at the level of cloudflare.
The single-sign-in options go through the techart.online domains, I think, because the website transitioned before Rob G gave us the old tech-artists.org domain rights. Some SSO options (google, I think it was) are not very friendly to multiple alternative SSO addresses.