I am using a U.S. Keyboard on a 16-in M1 MBP Pro, so F6 works just fine for me, as it does on macOS 11.6.7 on my M1 mini with its Apple Extended Magic Keyboard running macOS 11.6.7.
In System Preferences > Keyboard > Shortcuts > Mission Control, F6 is configured by default to Show Notification Center (e.g. Extensions) provided it is selected there, and not remapped to do some other keyboard shortcut.
The British Keyboard has the same function key symbol. This F6 toggle works whether I have the System Preferences > Keyboard > ☐ Use F1, F2, etc. keys as standard function keys selected, or not.
This is how extensions work in macOS. They are not intended to be Desktop, or directly accessible applications. You have the feedback link, but I doubt it will do any good as this is an Apple design decision.