Another angle is "how likely is it that refrigerant might be released?". For instance, with a ground source heat pump 'water furnace', the refrigerant is factory sealed loop, just like a refrigerator. I'm not super concerned about what refrigerant gets used there as it can be extracted when the unit leaves service.

But mini-splits? Mini splits with long runs carrying refrigerant?

There's been a move in the Boston area to put heat pumps in low-income buildings. They seem to have gotten around this by doing the install via window-mount units that saddle mount (single unit means factory sealed, no hoses).