Earlier quoted context omitted.
Due to it being a radio licenced by rule, the firmware in wifi devices is locked down tight. If it ware wide open FCC would revoke it's type acceptance. The only project that so far has managed to even partially use wifi hardware as a more generic SDR is nexmon[1] and even that is rather involved. Really cool project but not much heard since 2018. For just experimenting with modems across a noisy path one could just…
If i run linux can i modify the firmware? Also the regulations differ from country to country so this should be legal in some of the country.
There are some devices with open source firmware, so yes for some devices:
https://github.com/chunkeey/carl9170fw/ https://github.com/qca/open-ath9k-htc-firmware http://netweb.ing.unibs.it/~openfwwf/