Language switch key toggle has no effect when only one subtype is enabled

[sfrvn]

Steps to reproduce

1. Settings → Languages: leave a single subtype enabled (the default after first setup).
2. Settings → Preferences → Additional keys: turn ON "Language switch key".
3. Open any text field — the language switch key does not appear on the keyboard.

Expected

The key appears on the bottom row (next to the space bar), as the toggle promises.

Actual

The toggle is on, but no key is rendered. Toggling has no visible effect.

Root cause

SettingsValues#isLanguageSwitchKeyEnabled() gates visibility on the
behavior preference (PREF_LANGUAGE_SWITCH_KEY: internal / input_method / both):

if (!mLanguageSwitchKeyToOtherSubtypes) {
    return imm.hasMultipleEnabledIMEsOrSubtypes(false);
}
if (!mLanguageSwitchKeyToOtherImes) {
    return imm.hasMultipleEnabledSubtypesInThisIme(false);
}

App version
Version 3.7.9

Device:

• Model: Samsung Galaxy A36
• OS: Android 16 (One UI 8.0)

[LeanBitLab]

isn't hiding the switch key when there is no language to switch better, its not a bug but intentional behaviour