Minority Suspect
-Kyogre is confirmed not to get Freeze Dry
-Xerneas is confirmed not to get Earth Power or Heat Wave
Anyways Primal Groudon (assuming it can't hold an item i.e. has to hold a Mega Stone-esque item) can still be checked by some of the usual Groudon checks:
-Cresselia (not 2HKOed by anything except +2 Fire Punch, can abuse Desolate Land to recover 66% health with Moonlight, can Toxic stall) (loses to pure special sets)
-Lugia (it actually used to run Reflect in Gen 4 for SD Groudon and it might do so again)
-Arceus-Ground (it can take a hit and do a lot of damage back with Earthquake or Judgment, not a hard check though unless you run a lot of bulk)
-Giratina-Origin (survives most attacks and can inflict a lot of damage back with Draco Meteor)
-Regular Groudon (if it doesn't have special attacks)
-Mega Rayquaza (Delta Stream gives neutrality to Stone Edge)
-Landorus-T (no Overheat)
It's also not too hard to revenge kill if it doesn't have a RP boost since its slow and still only has middling special bulk.
That being said, a lot of old checks (Grass Arceus, Skarmory, Giratina-A) just flat out don't work anymore due to the Fire-typing, and not being able to be burned is a huge asset. Heck, Primal Groudon counters Arceus-Water now lol. This is definitely an insane Pokemon and will probably one of the (if not the) most used Pokemon in Ubers along with Mega Rayquaza.