C6300 some devices connect only to guest wifi

All older devices that I have purchased before 2013 can connect to both main Wifi and guest Wifi networks (OS currently in use on those devices are Ubuntu 20.04, Windows 7 and Windows 10). All more recent devices (4 android phones, 3 android tablets, 1 linux laptop, 1 windows laptop), roughly from 2016 to now, can connect only to the Guest Wifi network, but not to the main Wifi. In android when connecting it says "password saved" but doesn't connect. In Linux (ubuntu 22.04) it goes in a loop of authentication failed, In Windows 10 same behavior as android. All the devices behave differently when using a wrong password, so the password is surely correct. I already tried to change password, removing MAC access control, change wifi channels, try 2.4 and 5 GHz, being the only device trying to connect, clearly rebooting. The model of the cable modem/router is C6300, firmware version 3.01.14, ISP is comcast.