Is there a way to change the file naming so that it puts (e.g.) MAV3 as the prefix to the file names instead of DJI_ ?

That would be a welcome change! And so easy to do. Pretty much every camera system has this feature.

No, it's not possible

Sadly its not possible on any of the DJI drones yet.

I use Lightroom.  It can do the name change.  And I was just pointed to Any File so I can import the SRT files.  Does anyone else save these or the LRF files?

If applicable and not ideal but you could perhaps use something like ''Bulk Rename Utility'' whilst the files are still on the card and the card is in a reader attached to a computer.

Would be nice if DJI implemented this as an option.