The adoption of the Resource Public Key Infrastructure (RPKI) is increasing. To better understand and improve RPKI deployment, measuring route origin authorization (ROA) objects, RPKI route origin validation (ROV), and RPKI resilience is essential. In this paper, we survey RPKI-related research that aims to understand RPKI deployment. Additionally, we enrich our survey with many industry and IETF-related contributions. Our work provides an in-depth analysis of the many ideas and challenges discussed in studies of the RPKI ecosystem and includes lessons from mistakes made in the past, which we should avoid in the future.