FWIW, I don’t think you need a fingerprint reader on your phone in order to use it as a login device, just some way of unlocking it (it’s possible that facial recognition or whatever mechanism you use to unlock your phone is sufficient). Essentially all you need is a way of unlocking your device’s TPM chip (Wikipedia page, Android-specific keystore implementation).
The way I have my neurons set up, my Internet Identity is only a hotkey for them, so I (or anyone else using my phone) cannot touch the neurons, ICP within or maturity. All I can do from my phone or laptop is vote with my neurons. The neurons themselves are controlled by a Ledger device, via a USB cable, in combination with a command line tool.
If you want to go really hardcore, there’s also quill, which you can use in conjunction with an air-gapped computer to manage your neurons. Of course, said machine does not need to be air-gapped, it’s just a good idea for it to be. Without that, someone hacking into your machine can steal your secret keys. Something that isn’t (or shouldn’t) be possible if your keys were e.g. stored inside dedicated hardware (TEE/SE/TPM) on your phone.