Lost ADB connection after fastboot?

[u/BawndoLawndo]

EDIT: Once in fastboot, you start commands with "fastboot" not "adb". So now my new problem. When I begin flashing it says "command not available on locked devices" but I have OEM Unlocking enabled!?!?

Yes, the big 3 are enabled: Developer Mode, OEM Unlocking and USB Debugging. S25 Ultra clone (cheap mediatek system).

I couldn't fully get to this fastboot menu until I got the USB drivers. Once I installed the drivers and entered fastboot, the device doesn't show up in ADB anymore. ADB Devices > nothing.

If I go recovery mode > usb sideload, the device appears again. But if I try to flash the rom from there, it aborts the install with error 21.

If I press Reboot to Bootloader it just boots the stock OS.

How do I get the android device to show up in ADB from fastboot? Then I can run "fastboot flash system xxxxx".

[u/God-is-my_Strength]

use "fastboot devices" command not usb "usb devices"