This hasn’t previously been a problem, when using XMLTV guided data (using xTeVe). Channel Logo url’s are not using HTTPS.
Channel logo url example: http://XX.XX.XX.XX:123456/images/8f8bcbea68dee0efd09b7c1dac927bb1.png
UPDATE:
The channel logos under Settings are loaded trough the PMS photo transcoder (proxy I think?). On the Guide page the RAW URL from the XMLTV feed is used, which won’t work.
It works, if the server hosting the XMLTV icons supports both http and https (my local NAS doesn’t). The problem seams to be, that PlexWeb changes http to https on these channel icons on the Guide page. Which means, that SSL is required now?
My bad. This isn’t a bug in Plex. This is caused by Google Chrome (v100) forcing SSL (https) on each request (works okay in Firefox). I’ll mark this as the solution, since it isn’t a PlexWeb bug.
Might be an idea, to use the PMS photo transcoder on these channel-icons on the Guide page (like on the Live TV & DVR setup page and on the frontpage Recent channels).