[burnt-resistor]

There is no grand conspiracy. Every major gaseous hydrocarbon also tend to usable as refrigerants but tend to be extremely flammable, while most every chlorofluorocarbon tends to inflammable but extremely toxic under deflagration forming nerve agents like phosgene and acid vapors like HF and HCl. Thus, the primary tradeoffs are cost, flammability safety, deflagration safety, ozone destruction potential, and global warming potential.

The problems of conversion include in/compatibly of lubricants and refrigerants with seals and the density, boiling points, and latent heat of vaporization of replacements. The R-12 to R-134a conversion process was simpler but typically included different lubricants, orifice, and o-ring seal materials. I don't see how R-12 to a hydrocarbon or admixture of R-290/600a isn't a magical tall tale without proper math, equipment, and understanding of HVAC operating principles.

See this PDF for a summary: https://www.colmaccoil.com/media/394090/refrigerant-guide-fi...