Since the awful last Player update which I hate btw, I can’t find any settings about the aspect ratio? Everything is now playing full screen and the side are being chopped off, they all play fine with VLC. I presume there’s an aspect ration setting somewhere but I can’t find it anywhere after a lot of searching.
As far as I can tell there’s no way in Plex to add a forced aspect ratio. You can do this though in a variety of video encoding programs that allow video passthrough - I used ffworks to batch export a 720x480 TV show in forced 4:3.
I know that with the Apple TV app, I get this issue but if you go to settings and tell it to automatically convert smaller video files, it fixes the problem.
This thread is about the “Plex Media Player”.
This is not an umbrella term for all Plex clients, but a separate software Plex player for installation on computers.
Therefore all of the above doesn’t apply to smart TVs or other playback devices.
Just to answer the original question - and yes, PMP is still awful - but you can murder the aspect ratio by switching to TV Mode, go to settings and from there you can assault the aspect ratio.
You can also attempt to fix a horrific encode with those same settings - might work, might not.