nginx ouvindo no ipv6, mas por algum motivo os sites não carregam

Estou tentando fazer com que o ipv6 funcione no nginx (nginx/1.19.6) para SSL. Nas minhas configurações de domínio eu tenho:

server {
    listen      93.93.135.169:443 http2;
    listen      [::]:443 http2;
    server_name backups.myserver.com;
   ....
}

..e então para a porta padrão;

server {
    listen      93.93.135.169:80;
    listen      [::]:80;
    server_name backups.myserver.com ;
    ...
}

O Netstat mostra o nginx como escutando nas portas 443 e 80:

 netstat -tulpn | grep nginx
tcp        0      0 93.93.135.169:80        0.0.0.0:*               LISTEN      1168/nginx: master
tcp        0      0 127.0.0.1:8084          0.0.0.0:*               LISTEN      1168/nginx: master
tcp        0      0 93.93.135.169:443       0.0.0.0:*               LISTEN      1168/nginx: master
tcp        0      0 0.0.0.0:9183            0.0.0.0:*               LISTEN      5247/nginx: master
tcp6       0      0 :::80                   :::*                    LISTEN      1168/nginx: master
tcp6       0      0 :::443                  :::*                    LISTEN      1168/nginx: master

Eu posso encontrar o servidor em ipv4 e ipv6:

root@admin3:~# ping -4 backups.myserver.com
PING backups.myserver.com (93.93.135.169) 56(84) bytes of data.
64 bytes from backups.myserver.com (93.93.135.169): icmp_seq=1 ttl=60 time=1.58 ms
^X^C
--- backups.myserver.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.575/1.575/1.575/0.000 ms
root@admin3:~# ping -6 backups.myserver.com
PING backups.myserver.com(2a00:1098:80:a0::1 (2a00:1098:80:a0::1)) 56 data bytes
64 bytes from 2a00:1098:80:a0::1 (2a00:1098:80:a0::1): icmp_seq=1 ttl=61 time=1.55 ms
^X64 bytes from 2a00:1098:80:a0::1 (2a00:1098:80:a0::1): icmp_seq=2 ttl=61 time=1.74 ms

No iptables , recebo:

iptables --list -n | grep 443
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            multiport dports 80,443

iptables --list -n | grep 80
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            multiport dports 80,443

..e ip6tables:

ip6tables --list -n | grep 80
ACCEPT     tcp      ::/0                 ::/0                 state NEW tcp dpt:80

ip6tables --list -n | grep 443
ACCEPT     tcp      ::/0                 ::/0                 state NEW tcp dpt:443

No entanto, quando testo o site em https://ipv6-test.com/ com http , funciona:

Mas assim que tento SSL, recebo:

Executando um teste de curl de outro servidor para ele, recebo:

curl -v -6 https://backups.myserver.com
*   Trying 2a00:1098:80:a0::1:443...
* TCP_NODELAY set
* Connected to backups.myserver.com (2a00:1098:80:a0::1) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: /etc/ssl/certs
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* error:1408F10B:SSL routines:ssl3_get_record:wrong version number
* Closing connection 0
curl: (35) error:1408F10B:SSL routines:ssl3_get_record:wrong version number

Estou ficando sem outras coisas para tentar. Alguma sugestão?