If I use the mic adapter(Hollyland-Lark 3.5mm TRS to c type cable), I can't hear the beep sound during the shoot start.
Is there a solution?

DJI Action 2 can hear both power on and off and shooting start beeps using the same microphone adapter.

Hi there. Thank you for reaching out and apologies for the inconvenience caused. Please note that the sound will not be affected even with a microphone attached. Kindly double-check if it is muted from the camera. To do so, swipe down from the screen, go to Settings, and then select the option to unmute it. If it's already unmuted and the issue remains, we need to collect some information for further checking. Please share a video showing the connection of the microphone to the camera, and the specific issue encountered. Please keep us posted. We appreciate your understanding and cooperation.