So I actually built one of the boards now. Only tested so far that it outputs 5V (more tests later). Still waiting on the common mode inductor (so jumpered so far). It was hard to find, but the one I designed it for is available at Digikey, part number 817-2151-ND (manufacturer Schaffner RN202-0.3-02-12M).
One tricky thing I noticed about the original design by sundberg84 is that he incorporates a thermal fuse. These are really tricky to solder and are normally crimped in production devices, e.g. for fans and such. If you hold the solder iron more than half of a second to the leg you will pop it (you will hear a tiny click when the spring releases) and you have to discard it. Now it isn't absolutely needed on this board, you could just put a jumper in place. But here is a trick if you want to solder a thermal fuse.
Don't solder any other components before the thermal fuse (makes it more easy). Take a small bowl of water and submerge the fuse in water while soldering it. Keep it submerged a while after soldering is ready, to let it cool down completely. This is a 100% reliable way to not destroy the fuse.
Here is a picture of the thermal fuse being soldered:
![Thermal fuse being soldered](image https://johanh.net/hlk/thermofuse_s.png)