Have you tried these troubleshooting techniques with NetworkManager not running? NM will fuck you up sometimes because it will change things with no indication of what it changes.

When you say you changed the channel, are you using a channel above 11 (for 2.4ghz)?

I had a WiFi card once that refused to use channels 12 and 13 due to having a built in regulatory database that was incorrect for my region.

1. What is the exact model or chipset on the card?
2. Have you confirmed it works on other liveusb distros?
3. Is your network using WPA3 by chance?

Have you checked the flags in wpa_supplicant? Some routers have non-default encryption schemes.

From my notes, use these USE flags as a test: net-wireless/wpa_supplicant wps wep ap fasteap eap-sim tkip uncommon-eap-types I’m pretty sure this is your problem :)

does your router have logs and are you able to see the authentication requests or connection attempts? (you could also try setting up another ap with the same bssid and settings to see if it also ignores that too).

without that and in your shoes; i would exactly duplicate the configuration and versions of your networking stack in your gentoo configuration; everything from the exact kernel version, to the module & firmware version; and onto the nmcli version and configuration. i would even compile the module along with the kernel if that’s what the live fedora was using.