This 2022 accessibility guide by Chelsea Nesvig & Kate Roché-Sudar from the University of Washington describes how to create accessible content for placing in the Canvas learning management system.
The guide describes terms like Universal Design, Universal Design for Learning (UDL), and Inclusive Design, as well as providing basic guidelines for content creation. Although some of the guidelines are specific to Canvas, much of the information is useful when providing accessible content regardless of its intended location.