A Study to Test Whether BI 1819479 Improves Lung Function in People With Idiopathic Pulmonary Fibrosis (IPF)

Inclusion Criteria: 1. Patients ≥40 years old at the time of signed informed consent. 2. Signed and dated written informed consent in accordance with ICH-GCP and local legislation prior to admission to the trial. 3. Diagnosis of Idiopathic Pulmonary Fibrosis (IPF) 4. On stable treatment with nintedanib or pirfenidone for at least 12 weeks or not on treatment with either nintedanib or pirfenidone for at least 12 weeks 5. Forced Vital Capacity (FVC) ≥45% of predicted normal. 6. Diffusion capacity of the lung for carbon monoxide (DLCO) ≥25% of predicted normal corrected for hemoglobin (Hb). 7. Women of childbearing potential (WOCBP) must use highly effective methods of birth control with low user dependency and additional barrier contraception for male partners (use of condom) until end of follow-up period. 8. Male trial participants with WOCBP partners must use contraception (condom) to avoid exposure via seminal fluid. Female partners of male trial participants must use highly effective methods of contraception during treatment until end of follow-up period. Exclusion Criteria: 1. Acute exacerbation of Idiopathic Pulmonary Fibrosis (IPF) within at least 12 weeks prior to screening and/or during the screening period (investigator-determined). 2. Treated with immunosuppressive medications (other than oral corticosteroids) or prednisone \>15 mg/day or equivalent for respiratory or pulmonary reasons. 3. Patients who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial. 4. The patient is currently enrolled in another investigational device or drug trial, or their Visit 1 occurs less than 30 days or 5 half-lives (whichever is longer) after completing a previous investigational device or drug trial or receiving other investigational treatments. 5. Patients with a significant disease or condition other than the IPF under study, which in the opinion of the investigator, may put the patient at risk because of participation, interfere with trial procedures, or cause concern regarding the patient's ability to participate in the trial or any medical condition which could lead to a life expectancy \<12 months. 6. Relevant airways obstruction (pre-bronchodilator forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) \<0.7). 7. In the opinion of the Investigator, other clinically significant pulmonary abnormalities. 8. Lower respiratory tract infection requiring treatment within 4 weeks prior to Visit 1 and/or during the screening period. Further exclusion criteria apply.