If you are an MSP or would like to whitelabel the DMARC interface it can be done with a CNAME record in DNS.
We will acquire an SSL certificate from LetsEncrypt.org (We are a multi year corporate sponsor of the LetsEncrypt project)
The login screen and the website URL will keep your branding as will the monthly reports.
White label settings are under the User Profile in the top right hand side. https://app.dmarcreport.com/users/edit
Click on instructions and you will be provided the DNS record you will need to create in order to enable white labeling.
If you are using Cloudflare DNS, make sure the "Cloudflare proxy" mode is disabled for all DNS records you added. Ensure the cloud icon is grey (disabled) and not orange (enabled). This prevents Cloudflare from rewriting the DNS records.