Actually the same question from my side. I try to get the GPS information from a video recorded on an Osmo 360. The .OSV files are in the end also just MP4/MOV files with the same data tracks .
While trying to find information on how to decode the information I found the following outdated whitepaper:

https://developer.dji.com/doc/payload-sdk-tutorial/en/advanced-function/media-file-metadata.html

But it didn't work for me so far.

For the Action 4 and 5 cameras, there is a project on GitHub that can extract the GPS data. Maybe this is something that helps you with the metadata you are looking for.

https://github.com/francescocaponio/pyosmogps

I try to get updated information about the media file metadate from DJI developer support. But they only told me I should contact the team maintaining the Whitepaper - without telling me how to do so.
So if there is anyone from DJI reading this - please point me to the right contact.