@GnuDos 

Not sure I understand?

GnuDos wrote

1. After installing IOS 14.0.1, encountered numerous internet issues. Was told by Apple that WPA2/AES or WPA3 were preferred.

I assume it all worked before installing the Apple update? What does 'numerous' issues mean? What Apple device is this? More importantly, what was the router Wireless Security set to?

GnuDos wrote

2. After getting the ISP modem straightened out, the router flashed a very brief message: IOS 14 from Apple requires WPA3 set

There is a lot of 'stuff' in the above statement, but not details? First, why did you need to change the ISP modem as it has nothing to do with how the Apple device connects? What are you not telling us? What have you changed?

Next, where did/could the router flash any message? I'll assume you saw this on the Apple Device?

It seems if you have LESS SECURE settings, the Apple devices WILL put up " WPA2/AES or WPA3 were preferred", and is it more of a warning.

Might want to look at these links:

https://discussions.apple.com/thread/251821635

https://discussions.apple.com/thread/251805737

It would seem your Wireless Security Setting is NOT WPA2/AES, but a different version (WPA-PSK/TKIP whick is less secure???). Fix this on the Advanced Wireless page of the router.