I’ll answer here directly, as the issue is with the H5P plugin for WordPress, not with the content type.
In order for gltf
/glb
files to be allowed, those file types need to be allowed in H5P core. That has been done in June 2021, but the H5P plugin for WordPress is being shipped with an outdated version of H5P core (having other issues, too). So, in order to make this work, either the H5P core team needs to release an updated version of the H5P WordPress plugin containing a more recent version of H5P core, or you’ll need to locate the file h5p.classes.php
and add the file type extensions that you require (gltf
and glb
) here https://github.com/h5p/h5p-php-library/blob/ab0085de2e2400ffb5bf45ddfafe3c43ab1e3d35/h5p.classes.php#L2024