Nice project! I always enjoy seeing what people have done with libraries I’ve made.

This function returns a Boolean, not an EthernetLinkStatus. While your code technically works because I purposely made LinkOFF zero (note that other libraries might define this enum value as something non-zero, eg. see here: https://github.com/vjmuzik/NativeEthernet/blob/cdf6b3a2b5d62559a7c76be5b9d3fa60cf9d686b/src/NativeEthernet.h#L60), you’re comparing two different types.

Either:

while (!Ethernet.linkState()) {

Or:

while (Ethernet.linkStatus() != LinkON) {

Remember that there’s technically also the Unknown value to consider; that’s why I suggest comparing to “not ON”.