Thank you for the tip! That does indeed work in the way you described it, many thanks!
I don’t know if this is as far as the solution will go for now but if it is… Plex UI developers/designers: please do better! I don’t consider having to switch back into the TV mode to configure an aspect ratio setting to be acceptable UX. You should be aiming to make the desktop and TV layout modes have as much parity as possible. Please bring the option and shortcut to switch aspect ratios into the normal desktop mode. OR work on making the TV mode actually be navigable with a mouse… WHY IN THE WORLD can’t I drag the playhead in TV Layout mode? There is no technical reason Plex couldn’t serve as a complete in-home and away from home streaming solution, but quirks like these are why I can never rely solely on it when at home.