Good luck getting approval for propane as a refrigerant in the US. I think it's recently got approved for small systems like 5k BTU or less but that's a really small window unit. (Sealed units that can never be serviced, this making more waste)
When the whole cfc ozone thing was the "crisis of the the moment" it was already known that propane was an excellent refrigerant and could have replaced r12/r22 in most applications with no modifications. Did we do that? Nope, we doubled down are more regulations for more expensive systems, because money!!!! and who cares if the new refrigerants have a greater overall environmental impact. If they used something simple, cheap and readily available like propane they could stop people from using these older units or from continuing to service them themselves.
When the whole cfc ozone thing was the "crisis of the the moment" it was already known that propane was an excellent refrigerant and could have replaced r12/r22 in most applications with no modifications. Did we do that? Nope, we doubled down are more regulations for more expensive systems, because money!!!! and who cares if the new refrigerants have a greater overall environmental impact. If they used something simple, cheap and readily available like propane they could stop people from using these older units or from continuing to service them themselves.