It is incredible how strenuous grappling can be. We had a series of 3 drills (or katas) that basically put together all of the moves up to BJJ blue belt, and you were usually sweating after the 1st drill and had 2 more to go. There is no way to do that safely now with Covid. Even just going through the moves usually has you huffing and puffing in close physical contact with each other.
Grappling is definitely one of those things that can drive that old saying, "When you can't breath, nothing else matters" ;-) I have tapped and have tapped out others, not because I/they were in pain, but simply because I/they couldn't breath. It is definitely an interesting application of focused weight and force, among other things.
I have seen people do non-contact kick boxing workouts, which may classify as a non-contact MMA workout perhaps, and you can certainly do things against a bag, which would not be person to person contact. Again though, the safety of that with the current state of things would be pretty risky. Especially if you're doing kiai's (quick expulsion of air from your lungs) during the workout.