The short answer is... No!
You can set your domain to cloak a Nabble forum, but it will still be served by Nabble and hence have adverts, unless you pay to have them removed.
There was a long term goal that would offer a version of the Nabble code to host on your own server, but that is not ready - and may never be. Nabble never got close to pricing such an option. We'll have to wait for a response from a Nabble team member for the current position.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.