My Logitech K800 has an Fn key. I never paid any attention to it till just now. It works in Linux Mint, but they don’t do anything I care about. Another problem is the awkward placement of the Fn key, and that I’ve never learned the F-key placement by touch.

They are on F1 through F12:

Home, which takes my current open tab to the home page in Firefox, it would be better if it opened a new Home tab.

Email, which opens the default email client. I don’t know if I can set Gmail to open instead of Thunderbird, probably, but I don’t use email much.

A magnifying glass icon, which I assume is search, but doesn’t seem to do anything.

An alt-tab app switching duplicate. The alt-tab key combo is easier to reach.

Two buttons for controlling the backlight brightness. Set once to the lowest setting and never use it again.

A button to check keyboard battery charge level. There’s a tray icon that does the same thing

A PC power button, which I didn’t try.

And four buttons for controlling a video player that work in VLC. There are already single-key shortcuts in VLC to do those things.

Also, I’ve tried in the past to come up with some use for macro key apps, and just haven’t been able to. They seem nice on paper, but I just don’t have a use for such things.

My logitech keyboard has regular Function keys and separate “media function keys” iirc

I personally enjoy the feel of the Apple keyboards, but this is by far their worst feature. At least under Linux, they default to the function keys with seemingly no tricks available to swap functionality. Then add in the worst placement of the function key requiring two hands for nearly any key combination involving them.

I really wish there was someone else making high end low-profile keyboards with mechanical switches like these.