… at the free tier.
No-IP lets you use your own domain for their “Pro” tier - $10/mo. I do realize that $120/yr is expensive - you said so in your previous message. I just wanted to point out that it’s not a matter of “impossible” but one of “too expensive”, which is a different kind of problem.
Dyn is the Oracle service, and yes, they don’t seem to allow you to bring in your own domain.
But that having been said, you don’t need to use a service built-in to your router. You can also run an app on something else on your LAN (maybe on your web server) to keep other DDNS services up to date. But, as with No-IP, I would expect that any other service will also require a paid-up account in order to use your existing domain.
But here’s another interesting possibility. Can you use a free subdomain-type DDNS host and add a CNAME to your normal DNS hosting that can make your existing hostname an alias to the DDNS hostname?
I’ve noticed that big companies do this for content distribution, so why not your site?
$ host www.apple.com
www.apple.com is an alias for www.apple.com.edgekey.net.
www.apple.com.edgekey.net is an alias for www.apple.com.edgekey.net.globalredir.akadns.net.
www.apple.com.edgekey.net.globalredir.akadns.net is an alias for e6858.dscx.akamaiedge.net.
e6858.dscx.akamaiedge.net has address 23.55.200.211
e6858.dscx.akamaiedge.net has IPv6 address 2600:1408:c400:1889::1aca
e6858.dscx.akamaiedge.net has IPv6 address 2600:1408:c400:188d::1aca
e6858.dscx.akamaiedge.net has IPv6 address 2600:1408:c400:1882::1aca
e6858.dscx.akamaiedge.net has IPv6 address 2600:1408:c400:1888::1aca
That makes sense. Of course, if there is a conduit, then they could run coax through that space to put it back. But I agree, that is going to be aggravating if you need to move heavy objects to expose the wall jack again.