After connecting everything and turning on the Smart Lights X1, the power LED doesn’t turn on, why?

If the board is connected correctly and you cannot see the power LED on, disconnect the power immediately. Please check all the connections and measured with a multi-meter the resistance between 3V3 and gnd in any port (\(I^2C\) or Serial). If the resistance is close to zero you have a short circuit somewhere in your board, please check your connections and any soldering you’ve made If the problem persist reach Technical support In addition, remember that this version of the Smart Lights X1 (V1R2) cannot receive 5V through the Serial port “5V” pin, see the Programming section.

Can I upload ESPHome directly from the Home Assistance setup running on my Raspberry Pi?

Yes you can, and actually this is one of the simplest and more effective way to upload ESPHome.

Can I upload firmware if I don’t have an external USB-to-TTL programmer?

At the moment, this is the only way in order to minimize the components costs. But don’t worry, in general its a procedure that should be done just once.

I read that it can control 12VDC led strips and 24VDC, which one is the correct?

The electronics onboard are capable to power the ESP-32 in a range of 6 to 24VDC, meaning that is just up to your LED strips: if you have a 12VDC LED strip, just choose correctly the power supply for delivering 12VDC.