Where is the favicon - is there any documentation around changing it?
I'm not talking about the instance icon, I mean the favicon (svg or ico? png?) which appears in your bookmarks if you bookmark a site.
I'm running in docker
Please let me know what information you need to understand my situation? or if there's anything I can do to help?
That favicon is related to the Lemmy client you're running -- nothing to do with Lemmy itself.
Check the documentation for that client. You will probably need to replace the icon in the docker container.