Mathematica 12.1 does not have a native way of handling S3 files, the AWSLink was removed.
Someone know where can I download it?
Today I use command line tool: https://stackoverflow.com/questions/8659382, but it does not work with Wolfram Cloud.
UPDATE
Where can I find the old AWSLink package with S3 interaction?
AWSLink: https://mathematica.stackexchange.com/questions/168057
ExternalStorage: https://mathematica.stackexchange.com/questions/218574
Related Question: https://mathematica.stackexchange.com/questions/160011
Stephen Video: Wolfram Video Archive: Live CEOing Ep 06: AWS Link in the Wolfram Language