The answer to the question posed in the title is “no.”
1 is what I’ve thought from the beginning. That’s the recommended and supported solution at this point.
I’ve seen action on discourse_docker recently about increasing support for ARM, I think, but it seems improbable that supporting the mail receiver in ARM is something that’s going to get added any time soon. But that’s just a guess. I have no control over the matter, and there’s a lot I don’t know.
The other would be to figure out how to get ARM to support the mail-receiver and submit a PR.
If you love, love, love ARM, then you could find some full-blown mail receiver with mailboxes and all of that and manage a bunch of mailboxes.