I just tested mine, and here's what I found (needed to reboot each time I set the resolution - also no HDR for Netflix):
4k2k-60hz = Netflix 4k / No HDR
4k2k-24hz = Netflix 1080p / No HDR
4k2k-smtpe = Netflix 1080p / No HDR / Aspect ratio was screwy
While I was testing this I also tested out the speeds from an ethernet adapter vs 802.11AC and here are the results of three tests (using the Netflix app - I couldn't find a speed test TV app)
USB 3.0 Ethernet adapter: 41.33Mbps / 43.95Mbps / 42.43Mbps
802.11AC: 69.30Mbps / 63.84Mbps / 63.25Mbps
Also I decided to watch an episode of Luke Cage on each connection and with the ethernet USB I'd get some buffering issues (it would drop to 720p/1080p) that didn't happen on AC.
And just to second what @
seymourtv said, disable the 'XiaomiLeanbackCustomizer' app.
Denon X6500H 7.2.4 -> LG OLED65C9P
Main: NVIDIA Shield Pro (2019)
Other Devices: Apple TV 4K, FireStick 4K Max (2023), Homatics Box R 4K
Retired devices: Zidoo X9S, Xiaomi Mi Box, All the old RPi’s