I never looked into it before since I don't have any UHD bluray discs. After doing a quick search it doesn't appear that AMD supports anything like SGX so you're basically SOL if you want to try and physically play an UHD bluray on your PC if you're running AMD or any Intel CPU of the 12th gen or later. Watching normal bluray movies works just fine on any system as long as you have a program that'll play bluray discs; I make use of Cyberlink PowerDVD to watch bluray discs on my computer.
I guess if you really wanted to be able to watch UHD on your PC you'd need at least a bluray drive and copy it to your computer. I use MakeMKV (it's free to use while it's in beta - I'm not sure when/if it'll come out of beta) and then Handbrake to covert it to .mp4/.m4v to be able to run it off my plex server.
A bluray movie is usually around 24GB; putting it through handbrake can bring them down to about 1/4th or 1/5th the size depending on settings you use (I use the HQ 1080p preset for bluray movies and then I set the Encoder Preset to VerySlow. It usually takes around 1-1.5 hours at this speed to put a bluray movie through Handbrake with my 5900X). I just ripped a bluray movie last night, the .mkv file was around 27GB, the .m4v file is around 6.5GB
Looks like an UHD movie can take upwards of 45GB. If transcoding it through handbrake brings it down at least 1/4th the size then you're looking at around 11-12GB.
I guess it depends on how much space you have for data storage. You could leave the file in .mkv format or take the time to compress it through handbrake. Since Plex isn't setup to read .mkv files so I have to convert them to .mp4/m4v. I've got just shy of 1000 movies and 35 complete TV series all taking up around 4TB of space. If they were left in .mkv format I would need around 16TB of space.
If you want to use MakeMKV you can find it here:
https://makemkv.com/
Here's a direct link to the free temporary registration key while it's in beta (the key usually lasts 2-3 months, then you'll have to come back to this link and get the updated key):
https://forum.makemkv.com/forum/viewtopic.php?f=5&t=1053