I use my Spectrum connected to two computers: a Monterey MacBook Pro via USB-C, and a Windows 10 PC via DisplayPort.
To switch between the two computers, I wake up the new computer, then ask the current one to put its display to sleep. (⌃⌘Q on macOS, which locks the session and put the Mac to sleep; and the power button on the PC tower, which turns off its video output)
The switch from the USB-C MacBook to the DisplayPort PC works every single time, albeit a bit slowly.
However! The switch from the PC to the Mac is fairly unreliable; something like 1 in 5 times, the Spectrum stays black for 10-20 seconds, before showing (IIRC) “No Signal”. At that point, disconnecting+reconnecting the USB-C cable fixes the issue, and the Spectrum shows video from the Mac.
Of note, this is with the Mac open—not in clamshell. Clamshell makes things far less reliable still, but that might be a bug with macOS.
The screen is a 144Hz 4K Spectrum running firmware 105.