We are able to successfully connect to the s3 bucket content in ArcGIS Pro, but not Drone2Map.
As you can see from this AWS console snip, there are jpgs and other files in this folder
But not when looking at it from the s3 acs connection file in Drone2Map, the contents are not visible.
In pro, the contents are available:
I tried a different s3 acs file with other contents, and tif files showed up.
Maybe the limitation is that Drone2Map cannot read for jpg files in acs files.