That's fair! I didn't know they were offering that. I think it's a recent development -- it's not generally available ("contact us"), and it seems more focused at enterprise-type deployments than end-user mail that your typical Fastmail/Protonmail/etc.
But for the original question:
> Is there any email hosting out there with support for JMAP?
Stalwart really isn't a practical answer, at least yet.
I much prefer POP, as I only send and receive emails on my desktop computer and I want to decide when I fetch new emails. Is there any way to make IMAP work more like POP?
fdm, imapsync, lots of similar alternatives. Synchronize email to your machine and then use any MUA, or even several of them, to read it from a local directory (Thunderbird also works AFAIK).
They can also remove email from the remote and keep just the local copy. Pretty much 1:1 with POP. I've been using this setup (with fdm) for probably more than a decade.
Is there any email hosting out there with support for JMAP?