M1 MacBook Air: No 4K@60Hz on Samsung LU28R55

Hi, folks!

I have a M1 MacBook Air (8-core CPU, 8-Core GPU, 16 GB RAM).

I just received a new Samsung LU28R55 display today, which sports 4K at 60Hz. To my surprise, I'm only able to get 4K at 30Hz. I tried the "Premium High Speed/HEC" HDMI to HDMI cable that came with the display with Apple's own USB-C Digital AV Multiport Adapter. I also tried with the HDMI cable that came with the 4K Apple TV. Both options only give me 30Hz. I've since purchased a HDMI to HDMI cable that delivers 60Hz (reviews report that it does do what it says on the tin, so I'm hopeful this will work). This will be delivered on Sunday, so I won't know until then.

Failing that, I guess I could go the DisplayPort route, in which case, which is the better option for the other end of the cable? DisplayPort to USB-C? DisplayPort to HDMI?

What I've also noticed is some lag with my Bluetooth keyboard (Logitech K380) and mouse (Logitech M330). I'm guessing this is due to the display being at 30Hz? When typing and using the mouse on the M1 MacBook Air display itself, there is no lag at all.

Finally, in the Display settings for the LU28R55 display, I'm unable to pick any kind of refresh rate or anything like that. I just have the standard options (as I would do on the MBA itself) for resolution i.e. Default for display or Scaled. Neither of these options presents an option to set the refresh rate.

I'm curious to hear of any solutions on this front, or if anyone with the same display and M1 Mac has the same problem. I'll update this thread as things (hopefully) get resolved.