Unfortunately, Red Hat does not certify individual hardware components like Network Cards. However, if you can find a system in the Hardware Cert List https://hardware.redhat.com/
that has your NIC, then you should be OK. Otherwise, new drivers are adding to the O/S with each update release. The post above is useful as well, replacing a network card should be minimal considering the other value you will get out of upgrading to a supported O/S.