That's good news then, it means it is possible.
You did the right thing when you used sudo when it said no permission.
However, the output redirect part (the > in the command) is tricky with sudo,
that's why tee is needed.
Binding keys is pretty straightforward with most keys. But the fact sudo is
required makes things more complicated as you don't want to have to punch in
the password every time you hit the key.
To try and get around that sudo requirement I wonder what would happen if you
took ownership of that file /sys/class/backlight/intel_backlight/brightness
The command to do so is sudo chown $(whoami):$(whoami)
/sys/class/backlight/intel_backlight/brightness
Then you could try to see if you can use the echo command without sudo to
change the brightness.
The keybindings can be set somewhere in System settings > keyboard > custom
bindings.
If this works we can make a startup script that will do that ownership change
on every boot automagically.
