How can I auto-mount an internal SSD without entering my password?

You can also configure this through a disk utility such as GNOME Disks, even while using KDE. Select the partition, open the mount-options editor, enable mounting at system startup, and make sure the option requiring additional user authorization is disabled. Review the generated settings carefully before applying them.

First check whether the SSD is encrypted with LUKS. If it is, adding an fstab entry alone won’t remove the password prompt—you’ll need a crypttab configuration as well, or another unlock method such as storing the key with a supported TPM setup. If it isn’t encrypted, fstab is generally all you need.

For a normal, unencrypted filesystem, the usual solution is to add the partition to /etc/fstab and disable KDE’s automatic-mount setting for that drive. Using its UUID and an appropriate mount point lets the system mount it during boot without relying on the desktop prompt.

KDE can be configured with a suitable polkit rule to allow mounting that specific internal partition without repeatedly authenticating. This is more targeted than broadly allowing every user to mount every disk, so the rule should be limited to the intended drive and users.