All default Mac function keys (F1-12 and "F13") don't work. I don't use them as F-keys, but as Macs default e.g. Mission control, Launchpad or Show desktop, Volume up/down/mute.
Every time I press one of them, it actually fires that action twice, this is noticeably when pressing Volume/Brightness/Key light keys, so when volume is increased pressing once, the indication on screen shows 2 volume steps. This also explains the problem with Mission control I had, both on MX Master 3 (mouse) and MX Key (keyboard), that the function struggle to perform the window animation. And this is probably due to that mouse and keyboard send the command twice in a row very fast.

Macbook Pro 14" M1 Pro, macOS Monterey
USB Unifying (Unifying is plugged into an integrated USB-A port on a LG Monitor, and the monitor is connected to the laptop using USB-C)