I faced same "challenge". Found how to download specific version. There is XML list of all versions (and their URL path): https://s3-us-west-2.amazonaws.com/dynamodb-local

I needed version 2.6.1. I opened https://hub.docker.com/r/amazon/dynamodb-local/tags and saw that 2.6.1 was published 2025-04-14. From this list I found the item:

<Key>v2.x/dynamodb_local_2025-04-14.tar.gz</Key>

and used that key in url: https://d1ni2b6xgvw0s0.cloudfront.net/v2.x/dynamodb_local_2025-04-14.tar.gz