I've recently learned that environment backups do not include Marketing Services or the data they contain. When restoring a backup, all interaction data and insights are lost. This means there's currently no possible way to backup marketing data and should an environment, where Dynamics 365 Marketing is installed, require restoring, all Marketing data will be lost.

This is a critical issue and will impact all Dynamics 365 Marketing customers and needs to be addressed as soon as possible.

It would be very useful to get a clear description of all of the things that will be lost and the things that will be retained in a backup, i.e., would email templates be lost or only the email clicks and opens etc. and what happens to Live Customer Journeys and Forms?

This is in reference to the following documentation- Manage marketing environments (Dynamics 365 Marketing) | Microsoft Learn