I have made early progress with getting Topfield RCUs to be recognised by KODI using basic LibreELEC key mapping. It requires an additional IR receiver unit, but seems to work OK on my LibreELEC VM thus far. Basic functions work, however, more detailed application key mapping and integration will be required at the KODI level.
More details can be found here: https://oztoppy.forumchitchat.com/post/remote-control-testing-12529503 (https://oztoppy.forumchitchat.com/post/remote-control-testing-12529503)