Open-source boards designed in KiCad by TurBoss on GitHub, from 3 repositories. A board’s address here is its repository’s there.
TurBoss/z80neo
z80neo, another z80 board
TurBoss/ZxIDE
ZX Spectrum 128K 2+ IDE Adaptor
TurBoss/ESP-MAINS-SWITCH
esp8266 mains switch