Elanga joined the Manchester United youth system aged 12 and won the Jimmy Murphy Young Player of the Year award in 2020.

He finished the COVID-shortened season as the Under-18s' top scorer in the league with seven goals in nine appearances, and won the Jimmy Murphy Young Player of the Year award.

Elanga made his first-team debut for United in a pre-season friendly against Aston Villa ahead of the 2020–21 Premier League season; he came on as a substitute for Marcus Rashford in the 75th minute of a 1–0 defeat.

[13] Elanga started once again, away to Wolverhampton Wanderers on the final day of the league season and scored his first senior Manchester United goal after just 13 minutes.

[27] Elanga chose to represent Sweden at a senior level, citing being born and having spent the majority of his life there, as well as the country meaning a lot to him as the reasons behind his decision.

[28] He was named in the international squad of Janne Andersson for the World Cup qualifiers against the Czech Republic in March 2022, where he also made his debut as a late-game substitute.

[29][30] Elanga scored his first goal at senior international level on 5 June 2022 in a 1–2 loss against Norway in a 2022–23 UEFA Nations League B game.