1.) Install ADB on your computer. ADB is the Android Debug Bridge, you find instructions how to do this on https://developer.android.com/studio/command-line/adb.html 2.) Open a command prompt and change to the directory where the adb executable is located (e.g. [Android SDK location]\\platform-tools). 3.) Launch an adb shell. Therefore, type "adb shell" 4.) In the adb shell, enter pm grant keepass2android.plugin.keyboardswap2 android.permission.WRITE_SECURE_SETTINGS and hit the Enter key. 5.) Type "exit" to leave the adb shell. 6.) Go to Keepass2Android > Settings > App Settings > Password-Access > Keyboard switching and enable "Auto-switch keyboard"
NOTE for Xiaomi devices: You might have to enable some settings before running the adb shell command, see https://www.xda-developers.com/keyboardswap-plugin-keepass2android-automatically-switches-keyboards-without-root/#comment-3432883576
Additional KeyboardSwap for Keepass2Andro Information