Support

No and I don't think we will ever be able to provide a version compatible with AWS4 :( The only reliable AWS4 implementation is Amazon's own SDK for PHP. This is over 2Mb of files. Currently Kickstart is about 350Kb. If we add 2+ Mb of files it will become impossible to work with, both for us (maintenance) and for you (performance). My plan is to remove the direct integration, for a very good reason: you can use the Import from URL to import from Amazon S3. It's slightly different but still possible and very easy.

How to import from S3. You can use Akeeba Kickstart with files stored on any Amazon S3 region by using a third party S3 tool such as CyberDuck. Using CyberDuck go to the directory where your backup is stored and right click on the backup. Choose the Copy URL, Signed URL (Expires tomorrow XX:YY:ZZ) option. Now go to Kickstart and click Import from URL. Paste the signed URL to Kickstart and Bob's your uncle!

A similar trick applies for Dropbox. Log in to Dropbox' site and right click on the file you want to import. Click on Share. There's a link to the file you can copy and paste into Kickstart. You can optionally set up an expiration date as well.

So, basically, the Import from URL is the only feature you need. I am going to document that.

I think that you could contact the CyberDuck author and ask him to add support for the AWS4 authentication scheme. It's still a new thing, Amazon didn't publicize the change very well and most developers are not aware of it. But having seen the strides made in CyberDuck over the last few years I am pretty sure that he will be more than interested to add support for AWS4.

Awesome! Open Source at its finest :)