It seems to be less common in America. And a bit random in Spain using hubiera and hubiese more interchangeably.

Yes, we use it. However, it’s more common to say “hubiera”. There’s no specific rule to differenciate between both, but at least in the center and north of spain we mostly use “hubiera” for first person and “hubiese” for third person.

“Ojalá hubiera podido ir, pero tenía deberes” (yo)

“Ojalá David hubiese venido, se lo habría pasado bien” (él)

As I said, both options would be correct in both cases, and probably in other places they use the words differently.

I don’t think it’s necessarily legal but it does sound more literary.