Hi Peter,
Thanks for posting the feedback but this seems to be a compatibility issue between versions of clients and RDC for iOS, and there is fewer things can be done to troubleshoot.
Per checking, the RD Client beta application for iOS on TestFlight is already full and someone already posted feedback that RDC beta crashed when typing Chinese.
https://remotedesktop.uservoice.com/forums/925639-remote-desktop-beta-client-for-ios/suggestions/41634457-the-app-crashed-when-typing-chinese
Kindly check if other remote application could help when waiting for the next update of RDC and also vote the feedback in user voice forum for product team to fix.
https://remotedesktop.uservoice.com/forums/265183-remote-desktop-client-for-ios/filters/new
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny