@ts678 Thanks again for your fast clarification… changelog… yeah.. should read that more 
Did another restore with --restore-legacy=true which ran fine, but got a warning which is unrelated I guess:
Warning: 2025-04-09 17:47:03 +02 - [Warning-Duplicati.Library.Main.Controller-OptionValidationError]: Der Wert "20250405T100003Z", der an --time ausgegeben wird, stellt keine gültige Zeit dar