Sabine Hossenfelder has a review of possible experiments that might give us information on quantum gravity. None of them are necessarily immediately possible, but a number of them may become possible in the near future. I don't really have any particular view on the subject,but I thought some here might be interested.

The article is at How can we test quantum gravity?

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.