"Use F1, F2, etc. keys as standard function keys on external keyboards" is not there for me.
iMac (M1, 2021)
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iMac (M1, 2021)
Explain, It's in your screen shot. If you are using a third party keyboard it may not be an option.
"Use F1, F2, etc. keys as standard function keys on external keyboards" is not there for me.