I actually end up using 2 mice and switching the keyboard from bluetooth (for the mac) to usb (for the linux) because I can't get usb working through the HDMI. And the screen is limited to 120hz (instead of 144hz) because of the switch quality or the HDMI cables, I do not know (it lights up and works for a minute and then goes black a few seconds every few seconds, losing sync).

In the end it is more tedious and less featureful than just plugging the mac to the screen via a USB to HDMI cable, switching everything from the screen (and doing the same mice / keyboard juggle than above), because at least I would get the 144hz and save the 150€ from the switch. I can't return it anymore because the 15 day window has passed so I still use it, it's a little bit easier to switch from the remote control than from the screen anyway, but that's expensive just to switch from a different button.

no monitor switching needed, although i did hook up a hub for more usb ports.