Advice for those who got inspired by this: don't repeat this design.

Author is doing the very ugly soldering job right next to 110V live wires. The ugly soldering is normally not a problem - we all started somewhere - but doing it next to live wires is a very bad idea. An unlucky bump, and you have a smoke and, if you are very unlucky, miniature fire on your wall.

A much better idea would be to either start from USB-powered device, so there is no live wires anywhere, or modify it to be 5V only.

For this particular case, if I wanted to reuse the device I already made, I'd simply remove the PCB and replace it with USB input. You don't even need any PCB in this case - just remove AC connector and green PCB, and put a USB input with a resistor that gives a pleasant brightness.

Or if you wanted learning experience, put a PCB with a ESP chip and make this light internet-aware. There there will be no need for smart plug behind it, it could talk to HomeAssistant directly. (As of now, the transformer-less power supply is not nearly powerful enough for ESP chip, but switching to external 5V input will fix this)