Mules were the prime mover in Italy. 1st Mtn Artillery had nine four-gun batteries of which only one was motorized (their AMF(L) battery) while the other eight only had mules. Each battery had eighty mules. The L5 is built to be broken into 12 pack loads. There are special saddle/harnesses designed for the specific parts (Canada didn't buy those) The balance of the mules carried ammo - saddles for those too (six rounds per mule if I remember correctly). Fun fact. It took the Italian army longer to train a mule driver conscript than ones selected as 2nd lieutenants or sergeants.
In Canada we used three prime movers in my day. The Airborne used the 3/4 ton cargo followed by the 5/4 ton. In 3 RCHA (and I think 5 RALC too) we had a 2 1/2 ton with a special portee kit so that the gun could be loaded in the back of the truck rather than towed. We usually towed them and rarely portee'd them except for road moves to Wainwright. In D Battery 2 RCHA which had the AMF(L) role, the prime mover was an M548 (the whole battery was tracked). The M548 also had a portee kit for carrying the gun internally. L5s were tricky to tow for two reasons: their wheel base is narrower than the tow vehicles which means they could fall into one rut or the other and tumble; and they didn't have wheel bearings just grease packed axle bushings which made high speed or long distance towing risky.
Mules. Although the Airborne battery once rented a donkey in Jamaica as a prime mover to tow one once. That metal stuff on the front top of the shield is actually a yoke that mounts on the folded trail rather than a towing eye to allow an donkey or mule or horse be harnessed to the gun.