> You don’t need firmware access to install malware on Android, so how many of stalkerware victims actually would have been saved by a locked bootloader?
With a locked bootloader, the underlying OS is intact, meaning that the privileges of the spyware (if you look in the right settings panel) can easily be detected, revoked, and removed. If the OS could be tampered with, you bet your wallet the spyware would immediately patch the settings system, and the OS as a whole, to hide all traces.
If someone brought me a device they suspected was compromised and it had an unlocked bootloader and they didn't know what an unlocked bootloader, custom ROM, or root was, I'd assume a high probability the OS is malicious.