If you have an SSL certificate so such a domain can serve HTTPS traffic if needed, which it wouldn't surprise me if some parking services generate for you these days via an ACME provider, then your domain will be in the certificate transparency logs so can be found that way.

One possible way around this is to use a wildcard and not serve anything on the base domain. Unless the right subdomain is listed somewhere, they'll not get any scans. Maybe useful for projects that you have online for just yourself and a small closed circle.