At International level Dingwall captained the Scotland U18 side qualifying through his Scottish father. Dingwall scored a try for the England under-20 team against Ireland in the final round of the 2018 Six Nations Under 20s Championship as they finished runners up. He was included in the squad for the 2018 World Rugby Under 20 Championship and started in the final as England finished runners up to hosts France. He was chosen to captain England at the 2019 World Rugby Under 20 Championship and scored a try against Wales to secure fifth place.