I can’t help regarding NCP and spdyn but I have good experience with AVM integrated “myFritz” dyndns solution NC not reachable over Domain (IPv6) - #2 by wwe together with splitbraindns for fast local access… I can’t really judge how it works with really dynamic public IP as here in Switzerland we got pseudo permanent IP so doesn’t changes frequently… but in my eyes the router is the best device to change the DNS record as it knows when to do so…