issue has been at least since November of 2022, it worked fine before and youtube is fine on everything else.
in the youtube app the following happens:
if i set roku display type to 1080 and watch 720 content on a freshly power cycled roku it's fine till you watch 1080 content then watch something below 720 is now pixelated instead of run through a quality resizer/upscaler. you can still watch 1080 fine but anything below is pixlated.
problem is someone missed a line of code in and update around 11/22 that only seems to happen when the display type is set to 1080, watching 720 content after watching 1080 content.
workaround 1 : buy a 4k tv as it works fine at that display type.
workaround 2: set 720 display type but then everything is 720 or below so gotta decide what you hate more, pixelated 720 or everything 1080 now 720 and below.
workaround 3: don't use a roku
my model roku ultra 4670x bought new in 2019 for $100 with 11.5.0 build 4312-46 youtube 2.22 build 110005090 connected via the integrated 100mbit ethernet on 300mbit internet
i can confirm the delete, unplug, plug in, reinstall and restore to factory defaults don't fix it.