[hans-moleman]

“ I will ignore the “powered from mains” requirement for this round of the board and feed in 5V elsewhere.”

I feel this will be a challenge. The wall wart is the size it is because that’s the size of a transformer/rectifier for 120/240 to 5v. Trying to add a Linux machine to that but keep the same size is the tricky part.

[dijit]

I’m sure there’s something that can be done with Gallium Nitride. The chargers coming from that method are many times smaller than the contemporary. Often you can get a 90w charger where a 40w charger used to fit.

https://www.howtogeek.com/509209/what-is-a-gan-charger-and-w...

[Epskampie]

The example he shows is pretty big (but not suspisiously big) https://miro.medium.com/max/720/0*jUoQD3Udknc9b5Lx.jpg

Since there are a lot smaller chargers out there this should still be possible. https://store.storeimages.cdn-apple.com/4668/as-images.apple...

[zibzab]

Transformers are fairly uncommon these days due low efficiency and large size.

You can build a much smaller (1-3 cm3) and more efficient system using more modern technology.

[fy20]

IKEA Koppla chargers would be perfect for this.

https://www.ifixit.com/Guide/IKEA+KOPPLA+Connector+(fix)/126...

I expect you could even fit a Raspberry Pi Zero inside if you replaced the charger electronics with something smaller.

[sokoloff]

Several smart plugs run OpenWRT already.