freedombone | home server system which enables you to run

You're not supposed to place your module file in /dev; it won't do anything useful by being there. You can put it wherever you want, but certainly you do have to insmod it. That might be an accidental omission from the manual, or they thought it was obvious enough that they didn't need to say it.

What you're supposed to create in /dev is a new special file, aka device file, with the major and minor numbers corresponding to whatever you used in your driver's source code, or whatever was automatically assigned by the kernel. You do this with the mknod command: sudo mknod /dev/mydevice c 123 45, where 123, 45 are the major and minor device numbers respectively. There's some explanation of this in Section 5.6 of the Guide. (Note that the example driver in the Guide apparently doesn't look at the minor number, so it can be anything you want.)

You should then be able to do something like sudo cat /dev/mydevice and have your driver's read function get called.

If there are unprivileged users on this machine, use the -m flag to mknod to give the special file more restrictive permissions so they can't access it, e.g. mknod -m 0700 /dev/mydevice c 123 45.

Strictly speaking you don't have to create the special file in /dev, and you could instead do mknod /other/dir/mydevice c 123 45, but it may cause confusion.

Depending on how your distribution manages /dev, the /dev filesystem may not persist across reboots, so you might have to recreate your special file on each boot. It may be managed by a daemon such as udev, and if you're going to use your device permanently, it has config files you can edit to ensure it adds your special file on boot. That is more a system administration than a programming topic, so head over to https://unix.stackexchange.com if you want to know more.