Arch, Raspian, Ubuntu, Ubuntu MATE, doesn't matter. It's just not cut out for 4k60 videos it seems. Even running the 64-bit OS.
@joeligj12 I did a quick search and it seems like running it off an SSD doesn't make much of a difference for streaming and heavy web pages: https://www.tomshardware.com/news/raspberry-pi-4-ssd-test,39811.html
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