Face ID
Can I sign into an iPhone XR with a password instead of Face ID?
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Yes. You will always have to have a passcode as well as Face ID. You can't only have face ID.
You can chose to turn off face ID and only use passcode however.
Here is how to change the passcode:
Use a passcode with your iPhone, iPad, or iPod touch - Apple Support
You can also change it to a custom alphanumeric code(password)
Good luck!