Has anyone embedded demonstrations into their online distance education mathematics courses? Have any of the ADA (Americans with Disabilities Act) or Section 508 requirements affected how you ensure accessibility for all of your students?
There are no fully accessible GUI math widgets. The closest is probably PhET https://phet.colorado.edu/en/accessibility. Sadly most people just say some text description is equivalent, which it is not. You should think about which accessibilities you want to provide, color adjustments, contrast settings, dark mode, screen reader compatibility, captions, keyboard control, mouse control, simplified text, ... then look for a widget and evaluate which are not supported. Just communicate with everyone so expectations are clear. Here is a report and app I wrote many years ago http://diagramcenter.org/accessible-dynamic-scientific-graphics.html