Honestly, almost entirely based on the fact that it’s a grassland and that it has a history with Jedi Temples in the EU(and also the saga), part of me had always assumed Luke’s temple was built on Dantooine, probably near where Arca Jeth’s Enclave was in Legends continuity.
Or Lothal? Abrams has avoided the old EU/Legends more than anyone else since the Disney buyout.