An in-depth qualitative interview study was conducted as part of a broader research project on safety assurance of Automated Driving Systems (ADSs) that can use machine learning to adapt during in-service operation. The interview study captured and analysed feedback from recognised leading experts from across the globe, which included a mix of both regulatory and industry stakeholders. The key objectives were to identify themes that could assist with the development of an ADS safety assurance framework, and to determine the level of support and feasibility for adopting these themes and the various safety assurance concepts and practices that they comprised. For each of the ten themes identified in this study, insights were gained from the experts regarding issues, challenges, and likely support for adoption. Of particular interest is where the feedback from regulatory and industry stakeholders aligned, and where they differed. The presentation will cover the findings from the expert interview study in detail.