On Windows 10 if etcher is failing to write (lets say ubuntu iso) to the USB thumb drive, with permission error, then we need to temporarily turn off Windows 10 Controlled Folder Access.
Windows 10 Controlled Folder Access Update
- open windows defender
- open virus & threat protection
- open ransomware protection
- turn off controlled file access
- Go back to Etcher and restart the usb thumb drive flash process. It should work now.
- turn controlled file access back on