Hi,
You don’t need to link your flip phone at all, Ruth, and it’s safe to just ignore that "Finish setting up" message if you’d rather not deal with it. If you’d like to stop the nagging altogether, you can go into Settings > System > Notifications > Additional settings and turn off "Suggest ways to get the most out of Windows", which is basically what generates those reminders. Another option is to remove or uninstall the Phone Link app from Settings > Apps, since it has no purpose without a smartphone. Both of these steps simply silence the prompts they won’t affect your actual internet connection or interfere with the way you use your PC.
Kind regards,