I have successfully changed the 4k video frame rate from 25fps to 30fps on the GX80 using this recipe:
Instead of using the [DISP] button, you should use the [PLAY] button.
1) Set your camera to P and switch it off
2) Hold down WB PLAY and AF/AE while turning on the camera
3) Press Playback (->)
4) In playback, press ISO and AF/AE lock at the same time while turning off the camera.
From now on the camera will display a a yellow exclamation mark every time you turn it off and you can record in 30fps.
Using this “hack”, I shot the following test video:
The video also tests the low light high ISO capabilities of the GX80. The darkest candle lit scenes are shot at ISO 6400 30fps f2.0. All footage uses i.Dynamic setting of HIGH, which leads to some ghosting on some of the scenes. Especially the close ups of the meat roasting on a stick. I think it is advisable to use a lower i.Dynamic setting when shooting at high ISO and consider using the 24fps mode in dark scenes to allow for some more exposure time (1/25 of a second is the longest exposure time at 24fps)
Switching to 30fps seems to remove a lot of the “Jitter” from the GX80, since almost all displays run 60fps natively and 30/60=1/2 while 25/60=5/12. And I guess nobody uses a 25fps PAL CRT TV to watch 4K!