This is actually very disappointing - I thought I had done my homework before joining Enjin for our community website and forums. I already had a domain I owned, and was ready for the move. I kept seeing the notes in several places about adding my own custom domain.
Well, I upgraded to Advanced, and added the custom domain and THAT is how I learned there was no way to secure my new Enjin community unless I switched back to the subdomain option. This is very disappointing as I said. As one other user mentioned, web admins should always care that their customers information is secure. It was only after I paid for a plan that I discovered this was not a possibility.
It looks unprofessional to me, to be forced to use a subdomain. If this were not a paid service, I could more easily understand. But when I am paying, I expect that at the very least my customer's logins and shop visits are secure. Not to mention, not having that https: will hurt you in search engine results.
So I am guessing that my only option is to switch back to the unprofessional looking sub-domain, and look elsewhere for my web and forum hosting solution. I was trying to avoid paying the larger upfront cost for a professionally designed site and forums install, but I prefer that to $9 to $30 a month for an unsecured website.
I hope they change this, but I am betting I'll have moved on before they get around to it.