So Kai Wong on his said a 3rd party cable was working for external mic.
Everybody was asking which cable he used and he answered on Twitter.

I just noticed the next day he added a "might not work tweet"
Anyway so I bought the cable and tested it with TRS and TRRS and different microphones:
Here are the results: and

IT DOESN'T WORK!
The second message "I'm not sure if it works or not" is really disappointing from him. He's supposed to be a pro and do serious reviews but he can't even try this seriously. Sad

Anyway if it can save you 11€!

Thanks, I was just about to order one

Thanks for sharing

Not being a microphone expert, I'm going to ask this question:  Is it possible that you have to use a different cable other than TRS and TRRS?

RichfromHowellNJ Posted at 5-24 02:14
Not being a microphone expert, I'm going to ask this question:  Is it possible that you have to use a different cable other than TRS and TRRS?

There is no jack for a TRS nor a TRRS on the Osmo Action just a type USB-C Jack.  

We will have to wait until DJI comes out with an audio adapter for the Osmo Action just as we did on the Osmo Pocket.

Bob

BobWinNV Posted at 5-24 18:29
There is no jack for a TRS nor a TRRS on the Osmo Action just a type USB-C Jack.  

We will have to wait until DJI comes out with an audio adapter for the Osmo Action just as we did on the Osmo Pocket.

Okay thank you for your response.  Patiently waiting for the adapter from DJI.