The promising teenager recorded an assist on his U18s debut at the age of 15 in a 2-0 away win against Wolverhampton Wanderers in August 2025.
The following month, Seldon netted his first goal for Chris Moore's side in a 4-3 comeback win away at Liverpool.
Seldon enjoyed a positive end to his maiden season at U18 level, recording four goals and two assists in the final six league matches of the 2025/26 campaign as Newcastle's youngsters secured third place in the U18 Premier League North.
Primarily a left winger, Seldon made his Under-21s debut during an EFL Trophy clash against York City in September 2026, featuring as a substitute in a 3-1 away win against the League Two side at the LNER Community Stadium.
Four days after his maiden outing at U21 level, Seldon made his first start for the young Magpies in a Premier League 2 clash against Leeds United, also playing at York's home ground.