Trouble with externel keyboard and ö ä ü etc.

Hi, I need help with missing characters when using an external keyboard.
Kodi runs with me on a nvidia shield under android tv, an external Bluetooth keyboard (ec technology, a40-bt002) is connected (but also ne logitech k280e via usb, same result) and delivers thanks to extended keyboard helper app on all apps on the shield(As file explorer, systemkeyboard input, mx-player, youtube, Google Play Store, DS video Synology, etc.) all German special characters like öäü € ° § but also many international special characters.

All apps is not quite correct: at Kodi (which otherwise runs on the shield really great and can be adapted very well to the needs of less technically oriented users), the keyboard does not öäü or ÖÄÜ. ß is available, also the assignment of the German keyboard with y and z as well as special characters such as # + -_ <> are accessible according to the keyboard layout.

In the language settings of kodi I have configured language = german, region = germany, character set = standard and tataturbelegung = quertz.
Almost arbitrary combinations of region, character set and key assignment I tried unsuccessfully: thumbdown:

The keymapping addon does not help

I have tried with the extended keyboard helper many unicode keyboard codes, a large number of international special characters is displayed with all other apps, but not with kodi

Also the Cyrillic ü (0x04f1) in the unicode character set is not displayed

I also experimented with double token unicode, no result

The umlauts can be entered via the virtual keypad, and üäö & Co is also available via the “kore” remote control app.

The problem was discussed in another thread, but not followed up

I have searched here and in other forums diligently, some to umlaut and keyboard problems, but there was no suitable tip.

Has anyone found a solution for the problem? So far, i would assume that this problem is not to be solved by configuration, there could be need of developmental bugfixing.