Ok, now I have a weird situation.
Wiring seems to be ok and I get the correct voltage from all the pins. However the ESP is not connecting to the WiFi. I can see the WiFi hotspot of the ESP but cannot connect (the password seems to be wrong). If I connect the ESP to the computer over USB, ESPhome does not recognize it. And now the strange thing. I un-soldered all the wires and the ESP works without problems on USB and on WiFi.
Is the wiring creating an issue?
I would guess either bad soldering or that A.C. 5V supply is not able to offer enough current.
Resolder carefully and test on breadboard like I suggested on previous post.
Also control with multimeter in continuity mode that you don’t have solder bridges on shifter board and that you have continuity on gnd pins.
One thing just came to my mind… If that level shifter module have pullup on data pins, esp8266 probably goes to wrong boot mode when using GPIO15 (D8) as TX.
So you can go with another pin like GPIO12 (D6).
Esphome has to use softwareserial since only GPIO13 and 15 can be used for hardwareserial. But at 9600 baudrate it should work.
Another option is to use TX and RX pins, but it’s hit or miss with D1 mini.
May I give you suggestion. Leave that D1mini to some other project, like blinking a led, and get some Esp32 devboards. Not some weird version but the old good Esp Wroom32 board with microUSB connector.