The lack of involvement of users with multiple disabilities or complex needs in accessibility research is a problem that needs further attention from the field. Designing and evaluating accessible technologies that accommodate the complex, multifaceted needs of users with multiple or profound disabilities can be challenging in many ways. However, the challenges related to conducting accessibility research with underrepresented communities are not discussed enough within the field. Motivated by this pressing issue, this report presents a summary of discussions initiated during the ASSETS 2022 workshop "Multidisciplinary Perspectives on Designing Accessible Systems for Users with Multiple Impairments: Grand Challenges and Opportunities for Future Research".