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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.
OK that makes more sense. But still. I'm sure it would have been possible to do that with only local resources. This is just a security nightmare waiting to happen, even if you don't care about the privacy implications.
My guess is that they wanted a single interface with a single codebase that works on all OSes, as long as they run a browser that supports it.
Having said that, they could just ship a HTML file and do it all locally instead of on the web. I still don't quite understand why they changed this, as the feature used to be built-in to their app.
I mean, someone like me would probably rather have them support Linux officially through some way rather than not support it at all...