There is one way. If you have care refresh just damage the drone and send it back for a replacement which will come with a much older version of FW, then just update till 0600. ;)
Here you go but need to use Drone Hacks app in Windows to downgrade it.
https://www.dankdronedownloader.com/DDD2/app/index.php?Brand=DJI&model=wm261&ver=01.01.0600&type=Aircraft