Also Pisound (https://blokas.io/pisound/) which has the benefit of built-in din MIDI, but without the active community sharing software (you kind of have to build everything yourself with PD or SuperCollider). Some people have gotten Norns running on pisound, but I could never get it to work.
This is a neat little box, but pre-soldered ones seem to be only available on the used market. There are bare PCBs out there, but I’m not very confident with SMD parts.
This is the thing that bums me out with DIY audio: people come up with extraordinary designs, do a limited run and then never (or rarely) make any more.
Norns is made and supported by Monome, and it is very much supposed to be a Product That You Can Buy... except unfortunately it's based on the Compute Module 3, which has been unavailable for a good while. They have been available in small batches occasionally over the last year, and hopefully will be more available soon.
Surface mount soldering is not too hard. I can't view the BoM on mobile, but from the photos the soldering looks achievable for someone with experience soldering through hole. Take a look at the document here https://github.com/monome/norns-shield/tree/main/bom - if it's mostly 0805 sized components you should be fine. Even a few 0603 would be okay if you have good vision and a steady hand.
> people come up with extraordinary designs, do a limited run and then never (or rarely) make any more
I never bought a milkymist. There are no more being produced. The design has never been updated for modern formats, such as hdmi. I have no clue how to design hardware.