Dualboot with same nc directory permission problems

Hey there,
i have a dual boot Kubuntu/Windows system, an additional data ntfs partition used by both and a managed nextcloud at hosting.de. I would love to sync from both operating systems with the same directory on that data partition and the clients seem to detect the files perfectly (no unnecessary syncing etc).

BUT the clients will create the new synced files with their user permissions which does not include automatic write permission for the other operating system. I can bypass that by giving the client another umask setting on linux, but dont know how to handle on windows. An completely different approach would also be very welcome :wink:

Any ideas on this?
Thank you very much for any answers!