Use a DP 1.4 switch: https://www.amazon.com/Angusplay-DisplayPort-Switch-Bidirect...

I tried ConnectPro's DP 1.4 KVM and the display blacked out constantly in MacOS. Friends who purchased the same KVM ran into the same issue with displays that push DP spec to the limit like 3440x1440@144.

The switch I shared works just fine. From time to time (once every 1-2 months maybe) the display blacks out for a second but a computer restart does the trick, or reconnecting cables. Also make sure to get HBR3 displayport certified cables.