When will we be able to register .at top level domains with Route53

Hello there!

Currently for the NEW TLD request you need to create a Feature Request via Customer Support (CS)/ Technical support (TS). I would suggest you to open a case with the CS for the same. There is no ETA as AWS does not publicize roadmap items, but you can check in periodically to see if this domain extension is available by reviewing these AWS documentation pages:

Domains that you can register with Amazon Route 53 -- https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/registrar-tld-list.html -- [1]

What's New with AWS? -- https://aws.amazon.com/new -- [2]

AWS blogs -- https://aws.amazon.com/blogs/aws/ [3]

That said, one way to use R53 (for better integration with AWS services, for example) without actually transfering the domain, is to update the name servers in your current registrar with R53 name servers. You can refer to the process here. [4]

https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/migrate-dns-domain-in-use.html -- [4]