Migration of Site Pages is not supported unless 'Allow users to run custom scripts' is enabled (4347887)

When migrating SharePoint sites or M365 Groups (with the "Migrate associated collaboration tools" setting enabled), you may notice that the Home Page is not migrating. You will also likely to encounter an warning similar to the example below:

Migration of Site Pages library was skipped. Migration of Site Pages is not supported unless 'Allow users to run custom scripts' is enabled. Please see the documentation.

There is a permission restriction that has been implemented in Office 365 that denies anyone to the "AddandCustomizePages" permission level.

This permission level is directly related to the Scripting Capabilities feature of Office 365 and has been disabled by default for security purposes.

1. Download and Install SharePoint Online Management Shell

2. Run "SharePoint Online Management Shell" as an Administrator

3. Execute the following commands to enable the "AddandCustomizePages" permission level on both sites at source and target M365 tenants, then attempt the migration again:

Connect-SPOService -Url https://domain-admin.sharepoint.com
Set-SPOSite https://domain.sharepoint.com/sites/SiteCollectionName -DenyAddAndCustomizePages 0

Note: Replace domain and SiteCollectionName accordingly, for example:
Connect-SPOService -Url https://metalogix-admin.sharepoint.com

Set-SPOSite https://metalogix.sharepoint.com/sites/Support -DenyAddAndCustomizePages 0