COVID-19 Football and basketball would be really hard since judgement plays a big role. A good ref learns how to make good non-calls that have no impact on a play and allows a good pace of play. Seems hard to program into AI. But using cameras or sensors for ball placement or in bounds/out of bounds seems like a good idea
Baseball is more cut and dry, or should be. I’d start with balls and strikes (and probably fair/foul), with a distanced home plate ump for plays.