Joplin Server does not have a favicon.ico stored in its webroot so no icon displays on the browser tab when viewing the web interface. Consequently, there will not be an icon associated with any bookmark. A GitHub Issue has been raised however at the time of writing it is still to be resolved.
The below method was found that allows a favicon to be inserted into the Joplin Server container so that a browser can use it. Additionally the icon is also inserted in a manner that survives the container being taken down and brought up again.
This was found using trial and error. I am in no way a Docker expert so if this is bad practice please let me know and I will delete this post.
In the folder where my docker-compose.yml file resides I created a folder caller server and placed a Joplin logo icon in it as favicon.ico. Using this folder is not a required step, it's just used to try to keep things tidy.
Then in my docker-compose.yml file I added a volume reference that links that icon file to the webroot in the Joplin docker container and calls it favicon.ico. So this volume statement is in the app: (Joplin Server) section NOT the db: (Postgres) section.
Extract from docker-compose.yml (below). Image used is due to being installed on a Raspberry Pi
...
app:
restart: unless-stopped
image: florider89/joplin-server:latest
depends_on:
- db
volumes:
- ./server/favicon.ico:/home/joplin/packages/server/public/favicon.ico
ports:
- "127.0.0.1:22300:22300"
...
After this a favicon appears when I access the server web interface. So far nothing appears to have broken!!