I had a Canon 5200 (I hope I remember the number right) and no matter what
I did I could not find a driver - all I could find is "not supported under
Linux". Fortunately the printer gave up before me and so I went and bought
an HP CP1025 instead and that works with no problems.

So I am afraid that your answer may well be that your LBP 3100 will never
work. Canon is not very sympathetic towards Linux (and, in my case, the
feeling is reciprocated).