When your server has IPv6-only, some services such as github.com without IPv6 are unreachable.
Use a free DNS64 server to reach these systems. Any VPN clients would also need to update their DNS server.
Internet server with a public IPv6 address
Look at https://nat64.xyz/ on your web browser.
Find the nearest location to your Internet server's physical location.
Example: Finland / Helsinki has a DNS server at 2a01:4f8:c2c:123f::1 and NAT64 prefix of 2a01:4f9:c010:3f02:64::/96 , close to the Hetzner VPS.
Log in to the IPv6-restricted server
Update your resolv.conf header; the changes to the header will not be overwritten.
vi /etc/resolvconf/resolv.conf.d/head
nameserver 2a01:4f8:c2c:123f::1
Apply the change using resolvconf:
resolvconf -u
Test with an HTTPS request to www.github.com; it should respond with a 301 redirect to github.com:
curl -I https://www.github.com
If you have a VPN client using the server, edit the wg0 network configuration to use the DNS64 server:
Log in to the VPN client.
Replace the Hetzner DNS server with the DNS64 address
vi /etc/systemd/network/99-wg0.network
#...
[Network]
#...
DNS= 2a01:4f8:c2c:123f::1
#...
Restart the network.
sudo systmectl restart systemd-networkd
Test with an HTTPS request to www.github.com; it should respond with a 301 redirect to github.com:
curl -I https://www.github.com