A PnP PowerShell write costs 1.2 seconds. Batching makes inserts 19 times faster and updates only 3 times faster, and only ten cmdlets support it at all. Measured, with the throttling and retry pattern that goes with it.
Find every site, list, folder and item that does not inherit its permissions, and who has access to it. With the full script, the Forms folder that breaks the obvious approach, and a PnP switch that reports success while doing nothing.
How to read lists, items and files with PnP PowerShell, and the things that come back looking nothing like you expected: 19 lists on a site with 3, person fields that are not strings, and a version history one shorter than the file says.
PnP PowerShell has fifteen ways to authenticate. You need three of them. Which still work after September 2024, which are dead, and the deprecated one that is still the only method needing no app registration at all.
PnP PowerShell scripts started failing in September 2024 when the shared PnP Management Shell app registration was deleted. Here is how to register your own app and get your scripts connecting again.
How to install PnP PowerShell, register the app registration it now requires, connect to SharePoint Online and confirm the connection worked. With the real output, including the two surprises everyone hits first.