I am personally not aware of any repos that are community-driven proving this integration. However, from the AWS doc
HTTP 500: Internal server error Possible causes: You configured an AWS WAF web access control list (web ACL) and there was an error executing the web ACL rules. The load balancer is unable to communicate with the IdP token endpoint or the IdP user info endpoint. Verify that the security groups for your load balancer and the network ACLs for your VPC allow outbound access to these endpoints. Verify that your VPC has internet access. If you have an internal-facing load balancer, use a NAT gateway to enable internet access.In referencing above:
Have you confirmed that your WAF has the correct entries? For the second part, have you verified that you have access to the token, and userinfo endpoint from AWS to Fusionauth?/oauth2/idpresponse?code=[xxx]&locale=en_US&state=[xxx]&userState=Authenticated.
The "Authenticated" part of your return URL is encouraging.
You can also view all FusionAuth logs (you may have already) here:
https://fusionauth.io/docs/v1/tech/troubleshooting/#logs
for additional clues.
Thanks,
Josh