Can you brine frozen meat?

No, you can't. Or at least, you won't get the result you're really looking for.

Water needs to be able to move through the meat for the salt and flavorings to be transported to the inner cells of the meat. When the meat's frozen, you're dealing with ice crystals.

... that being said, you can thaw the meat in the brine if you're desperate, but you have less control to know exactly how much salt will be absorbed. (and I vaguely remember another question on here about temperature & brining, and I seem to recall someone reported on experimental results that really cold brines didn't transfer flavors deeply into the meat.).

Yes, actually you can. Quite a few cooks will tell you it's very possible. I've done it, and it turns out great. https://www.thekitchn.com/did-you-know-you-can-thaw-and-brine-meat-at-the-same-time-tips-from-the-kitchn-216723