ddns is a little client which allows you to update your DNS zones with a record for the current machine. It's also a little server that lets you do the same thing, if that's your bag.
You can obtain one of the releases, or install it using Go (>= 1.14) with
go get github.com/bjjb/ddns
ddns -h
will give you information on how to use the command-line application.
It's probably most useful to run it with cron.
You may also run the server - see how with:
ddns start -h
It contains some sub-commands for controlling a running server via its API.