I get this message on an iPad but am not even connecting an accessory except to charge the iPad.
[Re-Titled by Moderator]
iPad, iPadOS 17
Check the charging cable and the power adapter. Either the adapter is acting like an unsupported accessory or the cable is affecting the ability of the iPad to identify it.
See >>> If you see an ‘Accessory may not be supported’ alert - Apple Support
If you are using a Smart (folio) keyboard, the alert is typical of a faulty folio keyboard. The electrical connections that pass through the flexible fabric hinges typically fracture - this usually resulting in errors and/or the on-screen notification that you see.
If applicable, disconnect the keyboard.
'Accessory may not be supported' alert appears on my iPad
