I finally received the boards from the manufacturer(big thanks to @Seeed-Fusion). I manage to assemble one board by soldering the components and such and...it WORKS(including OTA)! I will post the instructions on openhardware.io project page.

I see now that it was withdrawn from sales. This is the main supplier from where I buy components and from where that relay was bought: http://www.tme.eu/en/details/rm50-z-05/miniature-electromagnetic-relays/relpol/rm50-3021-85-1005/.

This site offers some alternatives: http://micros.com.pl/en/product/17467/p-rm50z005 . But please bear in mind that it's the 4 pins variant not the 5 pins one.

Hi,

Well the reason I used HLK-PM01 in the first place was because I had many laying around and actually this was the first AC/DC compact module that I bought when it first came out on aliexpress. I noticed that a 3.3V variant came out in the meantime but I didn't wanted to invest more and buy it. I have also many AMS1117/3.3V chips around so yeah...I think you know now why. This is a good combination also for reducing power supply ripple because it's a switching one type so a classic voltage regulator can reduce the ripple - well I'm not saying that the AMS1117 it's a very good candidate for this regarding PSRR but it has for sure some effect.

Hi,

I sent the design files for manufacturing last week so it will take about 2-3 weeks to arrive to my door. I know this may be a long time but unfortunately this is out of my control.