This message is “normal” in my understanding: I think it is because as a LineageOS based ROM it is using a combo of the device’s original source tree with iodé then running as a sort of containerize layer. So this is hwy the message that it is a “different operating system”. So you can have a “locked bootloader” (you wouldn‘t then have any “warning the device is unlocked and can‘t be trusted” message, but you would continue to have the “it is loading a different OS” message).