I have two AWS CloudFront distributions, one over an S3 bucket and one over an Application Load Balancer (ALB). On both of them I checked the box "Enabled HTTP/3". While using my application I noticed all my requests were running over http/2 so I checked my website with
curl --https3 https://my.website.com
and using https://domsignal.com/http3-test and got back that my site is not HTTP/3 compatible. The instructions from aws, CloudFront New HTTP/3, only say to check the box.
What else could I be doing wrong? I thought the one in front of an ALB might not be able to because the ALB only supports HTTP/1.1 and HTTP/2 but I would still expect my distribution in front of S3 to run over HTTP/3.
I'm not sure how else to test either, but any question, help, or problem solving tips would be appreciated.