Joplin Server is what we can self-host for free and "Joplin Cloud" is the paid-for sync server service that Joplin provides ("joplincloud.com").
From what I can tell they both started out the same. We got to self-host the software Laurent also used to beta-test and provide the Joplin Cloud paid service he offers. However there were updates to the server software that only really applied to Joplin Cloud. The reference to Stripe (above) indicates this work was to do with payment processing etc., something the self-hosted server does not need as it is for personal, non-commercial use only. So in GitHub there appeared references to "server-v2.x.x" and "cloud-v2.x.x"
The GitHub tags shows what @joplin_user noted, in that two updates have been made in the last four days.
So, in answer to your original question, yes, Joplin Server is still being maintained. Which is nice 
For those hosting Joplin Server on ARM it appears florider89 has already pushed the server-v2.9.2 docker image (along with an amd64 version) to docker hub.
EDIT:
Before anyone asks, florider89's docker image is one of the "unofficial" ones listed in this forum post.