To conclude several days later:
Could not get the 4k rips to play on the Roku client. I removed the Dolby layer per DreadPirate's instructions and remuxed the container from .mkv to mp4 but nothing worked. I considered reencoding the hevc file to av1 or something but didn't want to go any further.
So I got a 4k chromecast with jellyfin app and the movies worked perfectly (once I removed the Dolby layer as my tv does not support this).
So the Roku Ultra LT (2023) is perhaps not the best for streaming direct play 4k movies, which is a shame because I bought it because it had an ethernet port, which the chromecast does not.
-JR
Could not get the 4k rips to play on the Roku client. I removed the Dolby layer per DreadPirate's instructions and remuxed the container from .mkv to mp4 but nothing worked. I considered reencoding the hevc file to av1 or something but didn't want to go any further.
So I got a 4k chromecast with jellyfin app and the movies worked perfectly (once I removed the Dolby layer as my tv does not support this).
So the Roku Ultra LT (2023) is perhaps not the best for streaming direct play 4k movies, which is a shame because I bought it because it had an ethernet port, which the chromecast does not.
-JR