Comment by iam-TJ

Your git repository is not reachable over IPv6 despite publishing a DNS AAAA record:

    $ curl -v https://git.deuxfleurs.fr/Deuxfleurs/garage/issues
    *   Trying 2001:41d0:8:ba0b::1:443...
    *   Trying 5.135.179.11:443...
    * Immediate connect fail for 5.135.179.11: Network is unreachable

    $ dig +noquestion +nocmd aaaa git.deuxfleurs.fr
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46366
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 65494
    ;; ANSWER SECTION:
    git.deuxfleurs.fr.      6822    IN      CNAME   hammerhead.machine.deuxfleurs.fr.
    hammerhead.machine.deuxfleurs.fr. 6822 IN AAAA  2001:41d0:8:ba0b::1

This from an IPv6-only network. Since you publish an IPv6 record our DNS64/NAT64 gateway doesn't get involved hence the IPv4 immediate connect fail.