Well with the second amendment being interpreted as it is by the supreme court, that doesn’t seem like it could currently stand unfortunately. We do however require it for concealed carry permits in most states though, so at least that is something. We could also normalize gun shops give a basic multiple choice test before sales even without mandating it legally, as shops have the right to refuse sale to anyone if they seem sketchy (and often do refuse sales, but not often enough.)
Frankly I go a step further, we should make actors who don’t own guns but use real guns as props in movies should also be subject to learn at least Cooper’s 4 rules, like they do at most indoor shooting ranges on your first visit.