Hello DaniAJ,

Yes this will fit fine.

Your TV requires a VESA wall mount size of: 400 x 400 mm
The wall mount will work for this size 400mm x 400mm.
The maximum weight for the TV mount is up to 49 KG. Your TVs weight is less than 29 KG without the stand (feet).
So it will work fine...

You can see your TVs specs here: Samsung UE65MU9000 (65", VA, LCD, 4K, 2017)

The TV mounts specs here:
Goobay TV stand Basic Fix (Universal, 55", 40 kg)

Regards
Robert