For what its worth, here you go. Be informed that there are myriads of answers for this but hopefully it fits your current configuration.
Block Download or Offline Availability in SPO\OD4B
Site Level for SPO\OD4B
· https://support.microsoft.com/en-us/office/prevent-users-from-downloading-content-from-a-site-98821ec7-cc99-4393-a002-f73370ba6694 (Site Collection - SPO)
· https://answers.microsoft.com/en-us/msoffice/forum/all/use-onedrive-for-business-in-online-mode-only/36445916-c281-4d5c-8f0f-4a0e0916eafb (Personal Site - OD4B)
○ Additional instruction to access Library Settings: OneDrive Site > Return to Classic OneDrive (Lower Left) > Click the Gear icon > Show Ribbons
Client Level (Restrict Sync using NGSC)
· https://learn.microsoft.com/en-us/onedrive/allow-syncing-only-on-specific-domains (best for Local Workgroup or non-domain joined machine)
Please mark it as helpful if it does.