Scenario: 

OS X® 10.8.5 and other older macOS® releases are unable to connect to the WiFi and will show a ‘The Wi-Fi network “xxxxx” requires WPA2 enterprise credentials.’ if the default WPA2™/WPA3 Mixed mode setting is enabled on the following Linksys routers:
 

• MR7340
• MR7350
• MR7500
• MR9600
• MR9610
• MX4050
• MX4200
• MX5300
• MX8000
• MX8501
• MX8502
• MX8503

Solution:

To allow older incompatible WiFi clients to connect to the router, the only option is for the router to use WPA2 as the wireless security mode. 

Another workaround is to update the computer’s software, which might make it compatible with the WPA2/WPA3 Mixed-mode security setting on the router. 

If the computer still can’t connect after updating the operating system, then the issue might be the older hardware’s incompatibility with WPA2/WPA3 Mixed mode, in which case an upgrade to a new computer would be needed.