Navigate to System Preferences > Keyboard Settings to open the Keyboard Settings pane.
Click the Modifier Keys button and select the keyboard you'd like to configure
It's possible to convert the fn key to ctrl for your external keyboard, Macbook keyboard, or both!
To remap the fn key to ctrl in macOS, change the Function (fn) Key: dropdown to ⌃ Control. Then, press OK.
To change additional keyboards, simply select the additional keyboard from the Select keyboard: dropdown and repeat this step.
You're all done!
Because your MacBook is so important for all that you do in a day, it is important to take good care of your Mac battery, monitor your Mac's battery health, and check the cycle count of your Mac's battery when to determine if your Mac needs a new battery. This might sound like a lot of maintenance, but checking your Mac's cycle count is an easy way to determine if your Mac needs a new battery, and it's actually incredibly simple. A battery's maximum cycle count is how many charge cycles your Mac can complete before the battery is no longer able to perform and will need replacing. In this guide, I show you how to check your Mac battery's cycle count and determine if your battery needs to be replaced.