Since update to Firefox Quantum I can't install Mozilla suggested Add-ons.
Use Firefox: 58.0b4 (64-Bit) for Ubuntu canonical-1.0 Ubuntu 14.04LTS
The Add-On site shows me that I should download Firefox if I want to use this Add-on! There's no hint that the Add-on doesn't work with FF57 nor that its an old one. e.g. Greasemonkey
Could anybody help me?