This study is open to adults 40 years or older with idiopathic pulmonary fibrosis (IPF). People can join the study if they are not on any treatment for IPF are on stable treatment for at least 3 months before starting the study. The purpose of this study is to find out whether a medicine called BI 1819479 helps people with IPF. 3 different doses of BI 1819479 are tested in this study.

Participants are put into 4 groups by chance. Participants in 3 groups get different doses of BI 1819479. Participants in 1 group get placebo. Placebo tablets look like BI 1819479 tablets, but do not contain any medicine. Participants take the treatment for 6 months to 1 year. Participants are in the study for up to 1 year and 2 months. During this time, they visit the study site between 10 and 12 times and get up to 11 phone calls from the site staff.

At site visits doctors regularly perform breathing tests that measure how well the lungs are working. Researchers compare the results between participants who take BI 1819479 and placebo. The doctors also regularly check participants' health and take note of any unwanted effects.

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.

Once the criteria in section "Time Frame" are fulfilled, researchers can use the following link https://www.clinicalstudies.boehringer-ingelheim.com/msw/datasharing to request access to the clinical study documents regarding this study, and upon a signed "Document Sharing Agreement".

Furthermore, researchers can request access to the clinical study data, for this and other listed studies, after the submission of a research proposal and according to the terms outlined in the website.

One year after the approval has been granted by major Regulatory Authorities and after the primary manuscript has been accepted for publication, or after termination of the development program.

For study documents - upon signing of a 'Document Sharing Agreement'.

For study data - 1. after the submission and approval of the research proposal (checks will be performed by the sponsor and/or the independent review panel, including checking that the planned analysis does not compete with sponsor's publication plan); 2. and upon signing of a legal agreement.