Same Problem here after running latest upgrades on testing (4.12.0-1-amd64 - with two different machines).
On desktop machine the volume keys and terminal shotcut aren't working (STRG+ALT+T). On thinkpad the brightness can't be adjusted by using the FN+Keys. But pressing them ist registered by the system (i can set them at the keyboard settings). But it probably isn't a bug in cinnamon directly because it wasn't upgraded. Last upgrade before yesterday was at the 13th.
