Byrne signed a professional contract with Leyton Orient in the summer of 2021, following a season of training with the first team.[3] He made his senior debut for Orient in the EFL Trophy at home to Southampton U21 on 14 September 2021,[4] and subsequently played in three more matches in the tournament before Orient were knocked out by MK Dons in a penalty shoot-out.[5] He kept clean sheets in all four appearances.[6]