I can’t believe we haven’t had a flood of ‘grass needs cutting, should prune that bush, pick up the goal post that’s lying on the ground’ type comments.
Come on peeps, what’s wrong with you?
On a separate note, your bars are too narrow and you’re stem is too long 😀
On a serious note, have you tried the helmet mount? This wobble is pretty standard for GoPro footage (probably for all camera types buy I only have experience of the GoPro), but the good news is that that is as bad as it gets, i.e. your garden isn’t gnarly, but even on the rockiest of trails, it’s no worse than what you’re seeing here.