Upgrading existing emonbase (rpi3) to rpi4

I’ve got an emonbase dating from around 2020 or so communicating with two TX3 and four TH units, plus a TX4 over USB. Plus numerous other feeds arriving over MQTT.

As I’ve got several rpi4 boards now surplus to requirements, I was thinking of upgrading the hardware purely for speed purposes.

I’m guessing that all I need to do is to get a new RF hat to communicate with the existing kit?

Is that the one on available in the shop and how do I ensure it has the right firmware?

Or shall I try to desolder the existing one and transfer that over to the rpi4?