Are you sure? I tested ZIP code 55344 and the WFTC channels were available (Fox 9, MyNetworkTV, Movies!, and Fox Weather/FoxWX). (23.1 and 23.2 are available as well, but they show as The CW and Comet.)
If you select the check-boxes do you not have those channels available (they may not have auto-matched)? If not, it might be specific to the ZIP code you’ve chosen; try a more generic/regional one. If that works, you may need to report your specific ZIP code so Plex can have those channels added.