[3] Gnonto made his professional debut with Zürich as a substitute in a 4–1 away Swiss Super League win over FC Vaduz on 24 October 2020, and assisted his team's final goal.

[17][18] On 16 May, he set up a goal in Leeds's 4–0 win over Norwich City in the EFL Championship play-off semi-final, which allowed them to advance to the final against Southampton at Wembley Stadium.

[25] In May 2022, after being called by Roberto Mancini to join a training camp for the Italy national team, Gnonto was included in the final 30-player Azzurri squad for the 2022 Finalissima.

[26][27] On 4 June 2022, Gnonto made his senior debut for Italy in a UEFA Nations League game against Germany, coming on as a substitute and providing an assist in a 1–1 home draw.

[30] On 18 June, Gnonto started in Italy's 3–2 win over Netherlands in the third-place match of the tournament, contributing to Davide Frattesi's goal, who scored after the former's shot was blocked.

[32][33][38] His qualities and playing style have led him to be compared to English winger Raheem Sterling in the media; Gnonto has also cited his idol, Argentine footballer Lionel Messi, as a major influence.