I pinned the newer certbot package with omv-extras (if backports is enabled - you can disable backports in omv-extras) to allow creation of wild card certs. But installing python 3 is not an upgrade. It is installed side-by-side with python 2. So, it won't hurt to install it. I guess I will have to look at the plugin's dependencies though.
Unfortunatly, I can't see it… with or without backports enabled