In the image below I have limited the number of keys by blacking out the ones that, in my opinion, would not really be used for this (enter,arrows, hardware etc) and coloured the keys to be modifiers in gray. This will give us a nice starting point.

This gives us, 6 modifier (mod) keys and 63 normal keys (key), so to get the amount of two key combinations we can do key*mod
and get 378, call this A.
To get the number of three key combinations we have 6 mod keys and each can be paired with another, so each key can have 5 combos. If we do 6*5
we get 30 (com) and we can multiply this by key to get the number of three key combinations com*key
is 1890 and call this B.
Finally we can add A to B and get the number of mappable shortcuts for Unity, within the given criteria.
A+B = 2268
To summarize:
mod*key + com*key = answer
You should be able to use this on any keyboard by assigning the numbers to the variables (key, mod, com) by counting them and then using the final equation to work out the number of possible shortcuts.
I am no mathematician but I think I did this right, please anyone feel free to tell me if I am not in the comments but I had to answer this, it was driving me nuts.
Best Answer
Use
xev
to find out what the keycode is. MyControl_R
is105
. Then run this:If that works, head into the start-up applications dialogue and add a new entry to run that command on boot.