DDNS? How can I bring a “server” with a dynamic IP to the Internet without external services?

Question

Domain Name System

Good day. There is a nettop at home, from which I want to make a dev machine for pet projects, looking at the Internet, but the IP address is dynamic. I watched there are many services from paid to free, but I do not understand the principle of their work.
There was an idea that every N minutes it would be possible to go through the API to the hoster, get DNSs and see if the IP address of the machine matches, if not, update it, but updating DNSs is sometimes not the fastest thing .. A
couple of questions follow from this .
How do no-ip\ddns services work? (for example https://www.duckdns.org/ )
What alternatives do I have (my own - on my knee) besides these services and manually updating DNS zones? (something faster)

Answer 1

any ddns works very simply: periodically checking your address by the client and updating the a-record when it changes. plus low ttl for dns records.
Of course, you can fence your own, but if other providers have duckdns / free plans, it only makes sense out of interest.

Answer 2

Well, or https://freedns.afraid.org/

Answer 3

A small addition, dynamic dns services will help if you do not have Nat, that is, the address changes, but the ports are available.
Domestic https://Alviy.Com in the piggy bank of options