Well more to report. CPanel says:
"Thanks so much for reaching out. I know the mailman upgrade is definitely something many people are looking forward to, but it’s not something we’re able to support at this time. As uncomfortable as it is, the only current option would be to install MM3 and see what breaks. Since we have a minimum requirement for our consideration of their software (being able to migrate people in place), we haven’t done any testing, so it’s not possible for us to say what would or wouldn’t work.
Unfortunately you will have to make the best call for your customers, but without our testing I have to advise against trying a manual install of Mailman."
There is still the possibility of Discourse (suggested by a member of this forum). But it would require a hosted account somewhere as to host it oneself, you need VPS and something called Docker. I tried a free version of it on Disroot a while ago and it seemed ok, but the Disroot collective was very slow responding, plus you had to see other people's conversations. So while I wait for Mailman 3 on CPanel, this might be another solution.
Thanks.
PS... I am 66 and have lived outside the US since the age of 27. The language has begun to pass me by. The CPanel rep's use of REACHING OUT is a case in point. When I was in the US, you reached out to someone in trouble, Since I am in trouble, I do to feel I am reaching out to CPanel. I guess that is the nature of language change though.