Hello, We understand how important a strong Wi-Fi connection is. This article provides the available troubleshooting for Wi-Fi connection concerns. https://www.samsung.com/us/support/troubleshooting/TSG01001559
In reviewing the specifications for your router, it seems the router is designed to automatically connect you to the band most appropriate for your device. There may be a setting that needs to be adjusted in the router to allow to 2.4 and 5GHz connections. We recommend reaching out to ASUS for additional assistance.
If you are still unable to connect to the other bands, we recommend having the phone evaluated by an authorized service location. https://www.samsung.com/us/support/service/