The goal of this clinical trial is to compare REBUILD-SM (a purpose-built smartphone app and self-management package) with standard care in people with interstitial lung disease (ILD). The main question it aims to answer is: • Does REBUILD-SM improve health-related quality of life, symptoms, anxiety, self-efficacy and physical activity for people with ILD? Participants in the intervention group will work through the self-management package with support from a healthcare professional via phone or Zoom. They will also enter deidentified health data into the RE-BUILD smartphone app to track their progress over time. Participants in the control group will use a reduced functionality version of the smartphone app only. Researchers will compare both groups to see if there is any difference in health-related quality of life, symptoms, anxiety, self-efficacy and level of physical activity.