Yep there are already multiple heatpumps on the EU market that work with Propane. Interestingly, they are also marketed as "high temp", capable of emitting 75C water to drive normal aluminium radiators, similar to how a condensing boiler would.
In part this is due to how this still has a commonly accepted pressure ratio (vapor pressure at condenser:evaporator ought to be ~10:1 for fridge-like compressor designs to be happy), and in part because having the propane equipment outdoors and only interacting with water/water-glycol-mix for thermally connecting to indoors makes the safety aspects far easier. It's now hard for propane to sneak indoors, form a mildly concentrated puddle, any blow up from static discharge at the next opportunity.
Propane/air heat exchanger are normally dangerous due to difficulty of dealing with a leak even if you use a sensor to detect leakage of dangerous concentrations of propane into the air. At least if this is indoor air.
