I didn’t found that Add-on in my research, before starting creating my own, but after looking into letsdnsocloud, the goal of the Add-on is kind of different.
letsdnsocloud uses cloudflare and letsencrypt to make it possible to access your Home Assistant instance directly from outside. My goal was only to have a DNS which resolves to my Home external IP, so that I’m able to use VPN to connect to my Home Assistant instance. For that, you don’t need Letsencrypt.
On the other side, as small differences in the cloudflare implementation, this one supports the new API Tokens and ipv6.