Well, not sure about other options, but you could try remapping the multimedia keys to FN keys (and vice-versa if you don’t want to lose the multimedia key functionality) using something like Autohotkey (aka AHK).
Been a while since I last did it, but there should be plenty of tutorials/etc. about how to do it. As the mutimedia keys aren’t “standard” keys, you might have to do some kind of key-capture (you should be able to do this with AHK too) to identify – and remap – them.
Note: this might not work and/or need some tweaking to work in games and the like.
Alternatively (and less work), you could try tools such as Sharpkey or Keytweak (easy to find with your friends google or duckduckgo) 😀
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