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.
Logitech unifying recievers can work with any compatible product so you can add/remove devices to it. It used to be a standalone program to pair devices (looks like you can still download it) this replaces that program and the standalone option will probably be going away.
https://support.logi.com/hc/en-us/articles/360025297913-Logitech-Unifying-Software