I think a JPEG doesn’t typically have the coordinate system and geolocation info inside the file itself, so that would require the additional metadata files to uploaded with it.
The GeoTIFF also needs to have the coordinate system embedded so that Cesium ion knows how to correctly drape it on the globe. What is the original format that you got the drone images in? If it was JPEG were there any “.jgw” (Jpeg World File) associated with it?
Another way quick way to test this is if you can open the imagery in QGIS (or any other viewer) and it shows up in the correct location in the world then Cesium ion should be able to read it.