Access the network without logging into the captive portal on Android?
Make sure you have enabled root access for ADB in developer options
Connect you phone to your computer via usb or open a terminal emulator on your device (skip step 3)
Type adb shell to open a shell (Assuming you have adb installed)
Type su to gain superuser permissions
Tyoe settings put global captive_portal_detection_enabled 0 to prevent the Wi-Fi from disconnecting if there is no internet connection


Source: https://android.stackexchange.com/a/148442/62445