1. Create file data\functions\special\characters.mcfunction with

   say ÄÖÜẞäöüßêéè
   

2. use command

   /function special:characters
   

3. Chat:*

   [@] ???????????
   

*my first try worked correctly but after I changed from editing .mcfunction with notpad++ to windows editor the special characters broke. After that everything I tryed couldn'd fix it (new world; new function with notpad++; use /reload; don't use /reload;...)