I'd like to use ipv6, if only to avoid having to pay for an ipv4 address for some private vpcs (with public address for reasons). I remember having issues with fly.io as well, because they're ipv6 by default if I remember correctly.
Currently Denmark has worse support than I expected:
> Liste over danske udbydere (List of Danish providers)
> Internetudbydere på listen: 41 (ISPs on the list)
> Internetudbydere med fuld IPv6-understøttelse: 17 (41%) (ISPs with full IPv6)
> Internetudbydere med delvis IPv6-understøttelse: 10 (24%) (ISPs with partial IPv6)
> Internetudbydere uden IPv6-understøttelse: 14 (34%) (ISPs with no IPv6)
source: https://ipv6-adresse.dk/