This post explains how to embed charts in PowerApps/D365 Portals.
Get GUIDs of chart and view used in the chart
Navigate to ‘Web Templates’ and search for dashboard. By default, there would be a web template named ‘Partner Dashboard’ if we install Partner Portal. If we don’t have by default, we need to create it manually
Open the web template and update the source code with chart id and view obtained in Step 1
If we follow above steps properly, we should be able view charts in Portal.