micro:bit v2

Yeah, as I understand it the direction finding involves:

• The individual device sends a specially formed signal which repeats over and over
  
• A receiver with multiple aerials can then look at the phase difference between the aerials and can work out the angle.
  
  

However you need a special receiver for this. I feel like it was probably possible even before Bluetooth 5.1 if someone had a sufficiently advanced receiver.

How is going the Boufallo RISC-V implementation ?

It's not I'm afraid. I'm just spread too thin to actually start porting to new devices right now.