Intellectual2 You said that a long passphrase is inconvenient. I agree. You have to use it when the phone is in BFU mode (after a reboot), and you can use a fingerprint after that.
However, you mentioned that fingerprints can be risky if the government can compel you to use your fingerprint to unlock the phone. If your second factor is not just a fingerprint but a combination of both a PIN and a fingerprint, you now have the resilience of an impossible to brute force password for when the phone is in BFU mode (7 word diceware passphrase) as well as a very secure yet easy way to unlock the phone in your everyday usage (6 digit PIN + fingerprint).
I hope that makes sense. If not, let me know.