Almost nowhere that supports uploading GIFs supports APNG or animated WEBP. The back end support is so low it's close to zero. Which is really frustrating.
Do you mean services that reencode gif files to webm/mp4? apng just works everywhere that png works, and will remain animated as long as it's not re-encoded.
You can even have one frame that gets shown if and only if animation is not supported.
That's not the first frame, it's the fallback image that png decoders which are unaware of apng decode.
It is never shown by compliant apng decoders. You can make it the first frame of the animation, or any other image you want. e.g. some text saying "APNG unsupported"
