Must be superuser to mount - even though /etc/fstab option includes users

I am trying to set up the Automatic Ripping Machine (nickname for which, sadly, is arm) on a Ubuntu 20.04 LTS system with latest updates.

Part of the installation was to put the following line into /etc/fstab:

/dev/sr0  /mnt/dev/sr0  udf,iso9660  users,noauto,exec,utf8  0  0

And a requirement is that the mount point /mnt/dev/sr0 be created - this is where the daemon will mount the inserted DVD or CDROM. This has been created, as follows:

ls -ld /mnt/dev/sr0drwxrwxrwx 2 arm arm 4096 Sep  9 15:36 /mnt/dev/sr0

The issue is that, even though 'users' is set as the first option in /etc/fstab, the user (arm) gets error "mount: /mnt/dev/sr0: must be superuser to use mount."

As I read the documentation for /etc/fstab, it sounds like we should not see this message. I've also found indication (not at all clear) that this entry in /etc/sudoers will allow users named accordingly to perform mount. But it has not improved my situation:

arm ALL=(ALL) NOPASSWD: /usr/bin/mount, /usr/bin/umount

What must be done in order to allow a normal user to mount this device to /mnt/dev/sr0? (BTW: apparently I cannot configure a different mount point, but I'm not convinced that's the problem anyway.)