Hi,
I run my Joplin server through portainer/docker on my NAS. I thought to check for updates, and noticed last version is 2.7.4 from 4 months ago on docker hub, while the latest release on github is 2.8.8 at the moment if I see correctly? Are docker images not provided anymore for some reason? Or aren't releases after 2.7.4 stable yet perhaps?
v2.8.8 is still in "pre-release".
2.7.4 is the last release of the server.
It looks like there have been same changes to the server since then, so I would expect a release to come up once ready. In general the server doesn't update as often as the desktop app, so the github isn't a good place to check for updates, dockerhub is better.
Oh sorry, my bad. I thought I was looking at the server tags. I see the latest server- style tag is still 2.7.4.
Will wait for next one then 
There was a thread about the latest server version a few weeks back.