gnome files mounting local disk "not authorized to perform operation"

Open as root for editing a /usr/share/polkit-1/actions/org.freedesktop.UDisks2.policy file:

sudo nano /usr/share/polkit-1/actions/org.freedesktop.UDisks2.policy

Here we find the rule beginning with the following:

<action id="org.freedesktop.udisks2.filesystem-mount">

And at the bottom of this block, modify the following sections about this:

    <defaults>
      <allow_any>auth_admin</allow_any>
      <allow_inactive>auth_admin</allow_inactive>
      <allow_active>yes</allow_active>
    </defaults>

to:

    <defaults>
      <allow_any>yes</allow_any>
      <allow_inactive>yes</allow_inactive>
      <allow_active>yes</allow_active>
    </defaults>

Then save the file.

https://en.linuxportal.info/tutorials/troubleshooting/how-to-clear-the-not-authorized-to-perform-operation-error-message-when-automatically-attaching-USB-flash-drives-and-other-external-USB-storage-devices