Purchased new U-lock for newly rebuilt electric bicycle.  OnGuard 8000 Brute LS weights 1.9kg. As they explained in shop, for so heavy lock they have no bracket. Forum discussions reveal, that plastic bracket breaks within couple of weeks. So I found good use for  7x70 Carabine Hook. Rarely requested size fits exactly on bicycle luggage rack and other end fits for U-Lock bolt.

Covered the hook with cable sleeve to avoid rattle and tightened at rack posts. Lower part of U-Lock is fixed with simple Cable Clip tied to rack post. This bracket never breaks.