The things on your LAN that you're connecting to via DNS and IP, which cause the desire to have stable LAN IPs in the first place.

That's what DNS is for... to not need to remember or know numerical addresses.

And DNS is easier to set up if the IP doesn't change constantly.

This conversation is going in circles.

Okay, how do I properly set DNS so it tracks the changing public addresses of my desktop and printer? And I'd better still be able to use SLAAC.

You register addresses based on Router/Neighbor Advertisements in NDP. In your RA, you'd point it to your DNS server, which would then handle registration when hosts check in with their new IP addresses.

Which dns server supports this kind of dynamic dns in practice?

Wow look, DNS has the solutions!

How, exactly, pray tell, is "properly"?