All right, just recently got Debian installed on an old laptop. Did a pretty minimal install with MATE DE.

I was thinking this laptop had an intermittent issue with the onboard wireless controller where it may disconnect...thinking it did this when Windows was installed (which in that case, maybe the adapter was fine and Windows was the problem ) . I'll give it a good test run with Debian to see how it does...I have a USB wifi adapter as a backup. In the event if onboard wifi is having issues, how would I disable it so I can use the USB one instead?

And on a similar note, while I was test driving distros I noticed that the wireless manual switch on the laptop when turned off would turn off ALL wifi...both the onboard and USB adapter. I would've thought it only disabled the onboard wifi rather than both. Is there a way around this?

I know windows if you use that button on the kb and turn it off it is off and you have to use windows and that button to turn it back on again. I no longer bother using that button, I just leave turned on.

I wonder if you can catch the keycode for that and make it execute a more specific command (rfkill?).
If it's coded into the BIOS, probably not. But then you could check the BIOS if it can be customised.

If I have to end up leaving the button on that's fine. I didn't see any way in BIOS to disable it...it's a very low feature/option BIOS. I could see if a BIOS update might open anything up.

Been testing it decently now, and so far the onboard wifi is doing ok. Actually is there any way to do some sort of hardware test on the wifi?

Think hardware and simply disconnect the wireless card physically, is what I'd suggest.
Alfa USB wireless is a 2nd one.
Enjoy!

as root:
rmmod <adapter module> to disable
modprobe <adapter module> to re-enable
To make permanent create a <module>blacklist.conf in /etc/modprobe.d

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