I tried to use bless but it fails with: bless --folder /Volumes/Macintosh\ HD/System/Library/CoreServices/ --file /Volumes/Macintosh\ HD/System/Library/CoreServices/boot.efi --setBoot <> Could not determine partition for /dev/disk4s1 <> Could not determine if partitiion needs booter <> Error while updating booter for /dev/disk4s1 <> Unknown system type

Could be fixed by reinstall macOS via recovery mode. No data loss. BUt doesnÄt explain why Configurator 2 destroyed the boot sector.

Could not find any solution so far.

https://forums.macrumors.com/threads/install-macos-sequoia-in-utm-a-howto.2428780/