@gurusmi Im new to all of this and the Duet 2 WiFi was the first Duet board I got but it was a clone and could not connect it to save my life. I returned that and went onto the Duet 3 Mini 5+ after learning about it. Firstly you do not need the Duet 3 6HC unless you plan to use Nema 23's or 34's due to the 6HC standing for 6 High Current stepper drivers in this case TMC 5160's. The Duet 3 Mini 5+ is the best value and it has 5 TMC 2209's which are good up to 2amps I believe and is sufficient for the three 60mm Nema 17's and one 48mm Nema 17's I am running. Plus I could always add an expansion board and or daughterboard if I needed something more out of it but for a basic cartesian running 4 to 5 stepper motors the D3M5+ is the way to go IMHO but honestly also if I could afford it I would go with the 6HC granted I had some extra spending money. The feature I just figured out literally 30 minutes ago that helped me update my RRF from 3.2beta+1 to 3.3 was the fact that I could press the reset button twice really quickly which then would show the Status LED flash from bright to dim to indicate it is ready to flash the new firmware. A new drive will pop up on your PC (oh yeah the Duet 3 Mini needs to be connected to your PC via a Micro USB cable sorry lols) so after the new DUET drive pops up you can then use it to open it up and view what should be 3 files one of the files being named CURRENT.uf2 with the word CURRENT meaning the CURRENT RRF so anyways all I did was copy and paste the new RRF 3.3 onto the newly created DUET drive and then Status LED flashes really quickly indicating it is writing the new firmware onto the EEPROM I believe dont quote me on where it is writing to I just think it might be the EEPROM but anyways the new RRF 3.3 has been loaded and now I can finally connect my RPi 4b onto the Duet 3 Mini without issues now that the board is no longer running 3.2beta+1 wheeeewwwwwwww what a relief lols!!!!!!!!!
Good Luck!!!!!!!!!!!!!!!!!!!!