On 18 January 2022, Ullmann signed a contract with Italian club
Venezia until the end of the 2023–24 season. In January 2023 he joined
2. Bundesliga club
1. FC Magdeburg on loan. On 30 July 2024, Ullmann moved to
Wolfsberger AC on a one-season contract. On 12 November 2025, he joined
Grasshopper Club Zürich in the
Swiss Super League. He signed a contract with the Swiss record champions until summer 2027. Just eleven days later, on 23 November 2025, he was nominated to Grasshopper's starting lineup against
FC Basel and scored the opening goal in the 13th minute of the 1–1 draw. On 2 December 2025, he scored the opening goal in the
Swiss Cup round of 16 tie against
SC Cham and supplied the assist for Grasshoppers' second goal in the 2–1 victory. ==Career statistics==