I have seen some microphones with usb-c connectors on the internet. Is it possible to connect these microphones straight to the osmo pocket without using the 3.5 to usbc adapter?  

Hello and good day Jonathan Post IL. Thank you for reaching out and for the information you have provided. I hope that you will get the best recommendation from our valued DJI members with regards to this matter. Just a friendly reminder that DJI does not recommend you to use 3rd party accessories for your DJI Osmo Pocket. These 3rd party accessories might affect the DJI Osmo Pocket when in use. Actually, there is a possibility that these 3rd party accessories will be able work. However, since it's not yet optimized and tested by DJI we cannot guaranteed the stability of the said 3rd party accessory if it will work all the time with no issues. Thank you.

DJI Stephen Posted at 11-15 10:06
Hello and good day Jonathan Post IL. Thank you for reaching out and for the information you have provided. I hope that you will get the best recommendation from our valued DJI members with regards to this matter. Just a friendly reminder that DJI does not recommend you to use 3rd party accessories for your DJI Osmo Pocket. These 3rd party accessories might affect the DJI Osmo Pocket when in use. Actually, there is a possibility that these 3rd party accessories will be able work. However, since it's not yet optimized and tested by DJI we cannot guaranteed the stability of the said 3rd party accessory if it will work all the time with no issues. Thank you.

A external microphone is always third party, because DJI doesn't offer an external microphone. And DJI offers a 3.5 to usbc adapter to connect a third party mic, so.....

No. The DJI audio adapter must be used as it has security features buit in as well as being an ADC so other mics or adapters won't work.

Hi everyone!

Has anyone tested the Rode VideoMicMe C?

I am interested in this microphone and would like to know if it is compatible?

Normal microphones with USB-c connectors don't work on the Osmo Pocket. Those are ment for mobile phones and other equipment. BOYA makes two microphones with USB-c connectors specifically for the OSMO Pocket: BY-ME-OP and BY-DM100-OP
You surely will be able to google them. Both of them are relatively expensive so you might just as well buy the DJI microphone-adapter and use it with any 3,5mm connector TRS-microphone.  
BOYA BY-M3 OP
BOYA BY-DM100-OP