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As if it wasn't bad enough that they want me to use a random internet service to add a keyboard to a usb wifi receiver, they have the balls to put this for Firefox users. I clicked out of pure curiosity, as I'm not even remotely interested in involving a corporate internet service in getting my keyboard connected to my computer. This is the message you get now on Logi Options software if you have a Unifying Receiver: 
For the curious: https://logiwebconnect.com
EDIT: some people on the thread have brought up that the error message being displayed for Firefox users is due to the WebUSB API not being implemented by Firefox due to security concerns. This still does not justify having to use a web app to plug peripherals to a PC.
Problem are extra funtionalities. I have a MX Mastee 3. Works perfectly on Linux, but is has a additional Button for the Thumb. Can't be configured on Linux officially. There's a third party script called Logiops. It sometimes work, but it's not relieable either...
Ah yes, extra functionalities probably don't work on Linux, thats true. I have gotten so used to that but it would be frustrating if I just bought a very expensive MX mouse of course.
I have just stopping buying those things so in a way I'm missing out, but I also don't have to deal with this stuff. So its just pros and cons as usual.