https://h5p.org/documentation/installation/content-type-accessibility
Below is an overview of the accessibility status for the H5P Content Types. "OK" means that the content type has been tested and no known problems have been found. The goal is WCAG 2.0 AA support, so the content types have been tested against these criteria and more. The content types have gone through a lot of testing with various screen readers, keyboard navigation, zooming, code inspection and more. We can't, however, guarantee any level of accessibility support.
Do note that due to mistakes done by authors the example content(not the software) on H5P.org isn't always accessible yet. The example content some times don't have WCAG AA contrast, lacks subtitles and there are also other flaws not related to the software but caused by authors picking the wrong colors or not uploading subtitle files. This will be fixed, but unfortunately fixing especially the contrasts will be a lot of work since it requires completely redesigning or at least replacing all the colors in the example content to maintain the same aestetic quality with improved contrast.
Also note that Screen Reader testing has focused on open and/or free screen readers like NVDA and ChromeVox.