Just tried it on my linux box:

  * Trying 2a09:8280:1::a:791:443...
  * Connected to fly.io (2a09:8280:1::a:791) port 443 (#0) ALPN,
  * offering h2 ALPN, offering http/1.1 CAfile:
  * /etc/ssl/certs/ca-certificates.crt CApath: /etc/ssl/certs TLSv1.0
  * (OUT), TLS header, Certificate Status (22): TLSv1.3 (OUT), TLS
  * handshake, Client hello (1): TLSv1.2 (IN), TLS header, Certificate
  * Status (22): TLSv1.3 (IN), TLS handshake, Server hello (2): TLSv1.2
  * (IN), TLS header, Finished (20): TLSv1.2 (IN), TLS header,
  * Supplemental data (23): TLSv1.3 (IN), TLS handshake, Encrypted
  * Extensions (8): TLSv1.2 (IN), TLS header, Supplemental data (23):
  * TLSv1.3 (IN), TLS handshake, Certificate (11): TLSv1.2 (IN), TLS a
  * header, Supplemental data (23): TLSv1.3 (IN), TLS handshake, CERT
  * verify (15): TLSv1.2 (IN), TLS header, Supplemental data (23):
  * TLSv1.3 (IN), TLS handshake, Finished (20): TLSv1.2 (OUT), TLS
  * header, Finished (20): TLSv1.3 (OUT), TLS change cipher, Change
  * cipher spec (1): TLSv1.2 (OUT), TLS header, Supplemental data (23):
  * TLSv1.3 (OUT), TLS handshake, Finished (20): SSL connection using
  * TLSv1.3 / TLS_AES_256_GCM_SHA384 ALPN, server accepted to use h2
  * Server certificate:

...

Same on my macbook