https://cdn.satellite.earth/2754d7daa3c176a467e646bd0c779e85b85d8604ed1395e8e48412487ce4b5e1.3gp

I worked around it by uploading the video to Twitter first then downloaded it again from Twitter to upload it to Satellite and that worked as .mp4. As you can see it's much smaller after Twitter's reencoding and Satellite didn't change it to .3gp

..../7d3e0ab0c07e96751502ec76cb81bcc35f0a63a0e1ac850e8edb1c0b761071ff.mp4