Well, I have given up on HFR from my MBP but now I’m running into different problems. Every day so far now, my USB accessories have stuttered or stopped working with my MacBook Pro. I have a keyboard, mouse, and USB-C webcam plugged into one spectrum and an ethernet adapter and wireless USB headphones (Astro A50, specifically) plugged into the other (via a USB 3.0 hub).
What can I do to troubleshoot this? Unplugging and replugging the devices does not make them work, nor does turning off or unplugging Spectrum from power or from the MBP – I have to reboot my MBP to get the accessories working again.
So you were able to use 4k120 via a thunderbolt dock? Which dock? I assume it would only support one monitor at a time at that res, right?
I’m almost certain at this point that it is not possible to output 4k144 over a single USB-C cable from MBP without a dock or adapter of some variety. It’s not clear to me whether that is a MacOS or port hardware limitation. I’m also certain that it IS possible to output 4k144 via a USB-C to DisplayPort 1.4 cable, at least prior to Big Sur. I’m not sure why Big Sur didn’t like that configuration, but I’m aiming for a single-cable solution anyways so USB-C → DP is automatically a deal breaker. It’s also possible to output 5k/60 and even 6k60 over a thunderbolt cable to a thunderbolt-compatible monitor such as LG’s UltraFine 5K or Apple’s Pro Display XDR. Those imply the ability to output 4k/144 over a single thunderbolt cable – I’m not sure what the distinction would be though and why a USB-C device isn’t able to achieve the same rates.
I didn’t need to do this from my 16" MBP (2019) to get 4k/144 over USB-C → DisplayPort, FWIW. So YMMV, I suppose.
That cable will only do 4k60 in my experience. To get 4k144 from MBP you need a USB-C to DisplayPort 1.4 cable. If you’re cool with 4k60, then yes: with that cable you can power/charge your macbook pro and use it with the laptop closed (this is called clamshell mode).