FujiFilm GFX 100II Owner's Manual page 268

DISP ASPECT
Choose the aspect ratio used for the display of still pictures on
High Defi nition (HD) devices (this option is available only when
an HDMI cable is connected).
N
Choose 16 : 9 to display photos with an aspect ratio of 4 : 3 full screen.
The pictures will be displayed full screen with tops and bottoms
cropped out.
7
240
16 : 9
Options Options
The Playback Menu
4 : 3