What exactly is your question? R290 = propane is a common refrigerant today. So everything is fine.
Apart from that, the statement that other refrigerants will be banned from 2025 is currently nonsense. You can search for bans on PFAS and amendment of the F-Gas Regulation. You will see there that harmful gases / refrigerants are supposed to be banned - but this only applies to new systems. The planned regulations also do not provide for the replacement of an existing system. There is also the possibility of special quotas.
With propane, no matter how the discussion continues, you will definitely be on the safe side. In particular, artificial refrigerants are supposed to be banned. Propane or ammonia are, of course, substances.
By the way, propane is a dangerous gas. Highly flammable and combustible. The seller certainly did not mention this disadvantage ;-)
==> But don’t worry. The quantities in a heat pump are really manageable. Nevertheless, there may be requirements for indoor installation.
I personally would have no problem today buying a system with R32 (which is currently installed in most heat pumps). You can even refill it in the event of a leak at least until 2030.