[14] Spell Checker only uses first preferred system language
The built-in spell checker, part of the bundled AOSP Keyboard (LatinIME), only considers the current system language, not the selected keyboard language. For example, if you switch to German with AOSP Keyboard (or any other keyboard, when using the AOSP Keyboard spell checker), the spell check still uses English.
This is the same as #85 (closed) but it's back again in Android 14 because the previous framework-level fix is no longer usable. It would be better to fix this in the keyboard at this point. Other keyboard spell checkers do not have this problem (OpenBoard, Gboard).
Note that the spell checker needs to be selected separately from everything else, in Settings > System > Keyboard > Spell checker.