My new provider does not offer static ip4/ip6. DynDNS seems only to forward to native ips.
Using NC 27 - Mini PC - Router is currently FritzBox / Provider Vodafone (static ip). - Router will be speed port / Provider Telekom (no static ips)
For ipv4, you got temporarily a dedicated address that you could use with services like dyndns. Now, ipv4 are so rare, that they start to do a carrier-grade-NAT, so it is not a public ipv4 any more, just a private one. On these, you can’t forward traffic. Then you need to tunnel through VPNs, tunnel through TOR network, … or change the provider.
For the carrier grade NAT, you can test for that: ip.bieringer.net - Carrier Grade NAT Test Page
ipv6 on the other hand, that should work with dydns. Either it’s static or if it isn’t, you should be able to use services like dyndns. If you can run a setup in ipv6 only (meaning all your NC clients have ipv6 as well), this should work.
For my own home Nextcloud I have a very simple setup using a compatible domain /dns provider and ddclient on your server. With a simple and regular crontab, my domain is pointing to my changing public ip.
You’ll still have to configure the nat/pat of your router to forward to the Nextcloud or the frontal proxy.