I’m not sure what you’re asking.
Having a dynamic IP address is okay. You don’t need to replace your certificates when your IP changes, whether you’re using Comodo or Let’s Encrypt.*
Do you want to get a Let’s Encrypt certificate for
rvwing.eu? You can do that. The Comodo certificate doesn’t matter. You can have certificates from two CAs at the same time.
* Some CAs offer certificates for IP addresses. Let’s Encrypt doesn’t. I don’t know if Comodo does. But you probably don’t have one.