It is possible to customize the form of a SharePoint list using Power Apps.
Currently, if you change the URL of a SharePoint site they cannot be used anymore because they still link to the old URL.
Unlike normal Power Apps, after the URL was changed, it is not possible to manually change the data source to the new URL.
Therefore, such Power Apps must be deleted and rebuild from scratch.
It is possible to invest many hours customizing a form.
If it is required for business or legal reasons to change the URL of a site, it may not be reasonable to rebuild it from scratch.
Other "external" applications, like OneNote or OneDrive, can switch to the new URL automatically, so I suggest performing the change for embedded applications automatically, too.