but arduino has their own rp2040 nano which the pico also uses. so i guess it shouldnt be a problem, on top of that i have looked into wiznet5500 it uses SPI so there shouldnt be really any platform specific code.
I never said anything else. The Ethernet-Library should work. But you might do some other stuff on the board (other than networking) as this board is definitely not the best choice to implement a network only application.
The Arduino board using the RP2040 is quite new so not that many libraries already support that platform explicitly.