The USB keyboard suggestion mentioned in the other comments likely won't work either because of USB Restricted Mode. After an hour of being locked, iOS disables data over the Lightning/USB-C port until the device is unlocked. It’s a perfect, recursive failure: you can't unlock the phone because the character is missing, and you can't plug in a hardware keyboard because the phone is locked.

Treating the passcode keyboard as a transient UI element that can be "cleaned up" rather than a hard security dependency is a massive architectural oversight. If the OS allows a character to be used in a passcode, that glyph needs to be permanently accessible in a fallback mode, no matter what the localization team decides to prune.