I had similar issue with Emax 4in1 ESC. They were not beeping because my PSU was not providing enough current or voltage was too low. ESCs were 3-4S and I tried to power with voltage similar to 2S. I had some wired behavior. But generally if ESCs don't beep, it's not Librepilot issue. It's ESC internal issue. They should beep once you connect battery even without any flight controller connected.