As of November 21, 2021, the top 3 G..gle results when searching for "docker hub qgis server" are:
There is also a nice documentation on how to set it up natively: https://docs.qgis.org/3.22/en/docs/server_manual/index.html
But for those who are not much into configuring web servers, the learning curve may be steep.
Therefore, I am naively wondering; why isn't there an "official" docker image for QGIS server, by official, I mean maintained and published by QGIS.org itself and not by third parties?
Answer (2024-05-02)
As stated in this blog post by Anita Graser, there is now an official QGIS Docker image available at:
https://hub.docker.com/r/qgis/qgis
The code is available here:
https://github.com/qgis/qgis-docker
