Moodle complies with the Web Content Accessibility Guidelines (WCAG) 2.1 AA conformity for accessibility. This means that the programming already supports the accessible design of courses. Even more important is however the implementation of the content by teachers and course leaders.
Moodle contains (since version 3.11) the Brickfield Accessibility Starter Toolkit. Teachers can use this analysis function on request and receive tips on how to optimize their own course.
More information on how to avoid or keep barriers low within a Moodle course: