An USB isolator helps eradicate floor loops and minimizes electromagnetic interference (EMI) involving the computer along with the related unit. 1x GND 3V3 (P2 with 2 pins 2.54mm) connector may be used to power externally the WCH CH569 MCU (it is suggested to eliminate the P4/SHUNT in that case It's https://cesarsmdbr.blogdon.net/hydrabus-an-overview-49266274