How to really disable the native keyboard of a MacBook Pro when using an external USB-C keyboard?

I had an accident which has left several of the keys on my 2019 Intel i9 MacBook Pro not working. I am planning to take it in to my local Mac store to deal with the repair next month, however, at the moment, I cannot be without this machine... so I'm using an external USB keyboard.

Unfortunately... from time to time, some key(s) from the actual laptop's native keyboard seem to become locked in the "depressed" mode. I know this, because if I open a Text editor, I can watch as row after row of "ssssssssssssssss..." is being typed out. It is not only happening with the "s" key... btw.

So... until I can get this thing really fixed... I need to know how to disable... COMPLETELY... the native keyboard of this machine. I have looked online... and there are hundreds of articles that all talk about some "Old method" that involves the F1 key. For some reason, all of these articles seem to be equally as vague about what has changed... and why this is now such a difficult task.

I am running the most recent version of macOS. Ventura 13.3.1. So... apparently this "Old method" with the F1 key no longer works. Can someone please help me find some clear... step-by-step instructions on how to simply disable my laptop's keyboard?

And please note... if you mention using an F key... such as F1, F2... can you please be clear as to how I should access this key. Because on my 2019 MacBook Pro... one must press the Fn key in order to force the little multi-bar to change into F1, F2, F3... keys. So... if you say that I should press... Shift + F1 for example... does this ACTUALLY mean.. Shift + Fn + F1 (area) of the bar?

MOST IMPORTANTLY

Also... since some of my keys are not working... cab you please tell me how to do this using a USB-C keyboard. Because, I have a sneaky suspicion that the reason I've been unsuccessful so far is because some key(s) are not working for me to use a "Shortcut" to make this happen. I'd really prefer a "Click here... Click there..." method if possible.

THANK YOU ALL so much!!! I really appreciate this as it is causing considerable problems for me.