I cobbled together a bash script that used the cloudflare API to update the A record when my IP changed. It worked well.

Prior to that i used https://freedns.afraid.org which is free if you are willing to share your domain (people can create subdomains that point to their IP) or you can pay to keep it private. It's been around for a very long time, so it's unlikely to vanish. It's a very good service.