Multiple Project Dashboards from one standardised report

Please be careful with the terms Dashboard and Report - they have a very specific meaning in Power BI.

What I think you want is one dataset that you then want to use in different reports for different audiences. That is possible and is called a Shared Dataset.  You maintain the data once, and the various reports can consume it as needed (but they cannot modify the dataset).

Now - different audiences pretty much immediately means different workspaces. You will want to create separate workspaces for your distinct audiences, basically one workspace per project. That way users cannot switch to other projects unless you gave them permission to see that workspace.  (if you are on Premium capacity you are actually sharing apps rather than workspaces but the idea is the same.)

Note that nowhere did I mention dashboards - these are something different entirely.