A Study to Find Out How Nerandomilast is Tolerated, Handled by the Body, and if it Helps Children and Adolescents With Interstitial Lung Disease (FIBRONEER-chILD)

Inclusion Criteria: * Children and adolescents 2 to \<18 years old at Visit 2. * Participants with evidence of fibrosing ILD on high-resolution computed tomography (HRCT) within 12 months of Visit 1 as assessed by the investigator and confirmed by central review. * For children ≥6 years: Participants with forced vital capacity (FVC) % predicted ≥25% at Visit 2. * Participants with clinically significant fibrosing ILD at Visit 2, as assessed by the investigator based on any of the following: * Fan score ≥3, or * Documented evidence of clinical progression over time based on either * a 5-10% relative decline in FVC % predicted accompanied by worsening symptoms, or * a ≥10% relative decline in FVC % predicted, or * increased fibrosis on HRCT, or * other measures of clinical worsening attributed to progressive lung disease (e.g. increased oxygen requirement, decreased diffusion capacity). Further inclusion criteria apply. Exclusion Criteria: * Previous treatment with nerandomilast. * Participants treated with other oral/systemic PDE4 and non-selective PDE inhibitors within 30 days before Visit 1. * Participants treated with pirfenidone in the 8 weeks prior to Visit 1. * Unstable pulmonary arterial hypertension (PAH). * Active vasculitis, unstable or uncontrolled within 8 weeks prior to Visit 1 or during the screening period. * Any suicidal behaviour (i.e. actual attempt, interrupted attempt, aborted attempt, or preparatory acts or behaviour) in the past (lifetime). * Any suicidal ideation of type 4 or 5 on the columbia suicidal severity rating scale (C-SSRS) in the past 3 months at Visit 1 or at Visit 2 (i.e. active suicidal thought with method and intent but without specific plan; or active suicidal thought with method, intent, and plan). * Participants with clinically significant depression symptoms defined as the short version of mood and feeling questionnaire (SMFQ) score ≥8. Further exclusion criteria apply.