The promising teenager recorded an assist on his Under-18s 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 Under-21 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.
He scored his first competitive goal at second-string level during a National League Cup clash against Solihull Moors in October 2026.