As of a few days ago, Dronelink has a beta started with support for Mini 3 Pro and Mini 3. So clearly the DJI MSDK 5 with that support is available in some way, though the DJI dev site doesn’t show the version with M3/Pro support yet. Dronelink is having some issues with some phones and there may be issues with Android 13 at this point related to the MSDK.
It was also noted that DJI has obstacle avoidance disabled in MSDK 5 (unlike 4) which is a bummer. Dronelink says they’re pushing to have it enabled again and have some hopes this will happen.
As for installation on the DJI RC. Interesting to see that there may be a hack to get external apps on there. But keep in mind the memory resources and speed of that device are limited – running apps like Litchi on it (as opposed to a fast smartphone) may be impractical.
One other note: It appears DJI is only providing MSDK 5 support for Android, not iOS, at least at this time.