how do i disable the any key startup on the MacBook Air 2019

As stated previously, MacOS currently has no known way of turning this annoying feature off, but you can turn off the gimmick where if you open the lid when your Mac is powered off then it boots up, by entering "Sudo nvram AutoBoot=%00" into your terminal app. You can also revert this by entering "Sudo nvram AutoBoot=%03" also into your terminal app. Hope this sorta helps until Apple gets their crap together :/

I was reading about this on the web in general. Others have tried but this feature seems pretty deeply embedded.

How to turn your Mac on or off - Apple Support

https://support.apple.com/en-us/HT201150

"Additionally, MacBook Pro (2018) and the MacBook Air (Retina, 13", 2018) turn on when you press any key on the keyboard or press the trackpad."