How to update to Portainer 2.9.1?

It's very easy to update docker images automatically with watchtower-updater. You only need to run this SSH command once. From portainer you will start watchtower which will scan all the images that are not stopped, update them if necessary and stop again. Do this every fortnight. It is not a good idea to update automatically because sometimes some containers need to be monitored.

docker run -d \
--name watchtower-updater \
-v /var/run/docker.sock:/var/run/docker.sock \
containrrr/watchtower --run-once

Docker addons update when you reboot or do a disable/re-enable of the addon