glTF supports multiple animations in a single file, so ideally you’d export from the DCC tool with clips already separated (each starting at t=0), and get an array of AnimationClip objects back from GLTFLoader. I’m not sure how that workflow is best handled in Maya, but note that there are some Maya2glTF settings (-animationClipName, -animationClipStartTime, -animationClipEndTime) that you can use at least on the CLI to split animations. In Blender (which has a somewhat un-intuitive animation clip system itself…) I do this by “stashing” or making an NLA track for each Action to include as an animation.
If you find that you can’t split the animation and zero out clip start time at export, then yeah https://github.com/mrdoob/three.js/pull/13430 may be the solution and I can explain that further.