Just tested the OSR2-Ver3_4.ino with a clone Arduino Nano with only three servos wired up.
Tested with ayva-stroker-lite.io with Chrome - using USB - All working
and
tested with MultiFunPlayer - using USB - All working
Three servos is enough to be the “OSR2+” I would recommend 35KG servos with a strong power supply.
PUBLIC - MARCH 2022 Update OSR2-Release3_4
Tested with ver3.3.ino as well and that worked too.