Upgraded ipq806x/chromium from 24.10.5. I used system attend. I preserved my configuration and after reboot all Wi-Fi radios were unable to start or find a device.
I did a reset and then a clean install of 25.12.0 and I had the same issue.
I've reverted back to 24.10.5 and everything is working properly.
I've attempted this upgrade twice just to make sure I wasn't missing anything and I had the same results both times.
Can you provide an exact make and model of device?
(or the output of ubus call system board)
Just to be clear, OpenWrt's default config has all radios disabled for security. So, did you make any configuration changes after your clean installation (i.e., set country code, enable WiFi, set wireless security parameters, etc.)?
This should be added to the known issues list
See here for a workaround https://github.com/openwrt/openwrt/issues/21243#issuecomment-4061707020