Do you think that could be related to all these issues?
Edit:
God, you’re right. This has literally been bothering me FOR YEARS.
I run two Plex servers, so I don’t use the default port to avoid running into conflicts.
I switched one of them back to 32400 and the artwork loads instantly.
When I was testing I also tried using the manual connection settings and got the same result. Using any port other than 32400 means artwork doesn’t load.