Thanks a lot for your responses! None of your settings worked and I moved on to do a factory reset. I'm not sure where in the setup process this occurred, but I got a special IoT page asking to create a network for legacy devices! That's what I did and it worked 😅.
The asuswrt-merlin firmware...
Can anyone tell me what the most backward compatible 2.4GHz settings are for the Asus RT-BE88U router (Wireless->Professional in the web GUI) for devices that worked with WiFi 6 routers (Asus/Zyxel)? I know that it can work, because I randomly choose the correct settings, but I didn't write...