Installing Raspbian Buster Lite on the Pi4 isn’t an issue, download the image, put it on the sd-card, enable ssh access, and plug it in.
Oh the WiFi setup is a bit different if it’s required, but not a problem either.
Following that you just install the piaware stuff: PiAware - dump1090 ADS-B integration with FlightAware - FlightAware
Then you run airspy-conf and you are done with the setup: GitHub - wiedehopf/airspy-conf: Configure airspy_adsb for use with readsb or piaware.