Is there any way to prevent users on unmanaged/personal devices from downloading inline images in Microsoft Teams chats/channels?

The provided information only covers blocking or limiting access to SharePoint/OneDrive content (including Teams files) from unmanaged devices, and blocking downloads of files that are identified as malicious by Safe Attachments. It does not describe any control that specifically prevents downloading inline images delivered via Azure Media Services in Microsoft Teams chats/channels.

From the available details, the following controls exist:

1. Block or limit SharePoint/OneDrive access from unmanaged devices
   • Organization-wide or per-site/OneDrive policies can be configured so that users on unmanaged devices have web-only access and cannot download, print, or sync files.
   • This is done via:
     • SharePoint admin center → Access control → Unmanaged devices → Allow limited, web-only access, or
     • PowerShell: Set-SPOTenant -ConditionalAccessPolicy AllowLimitedAccess.
   • Site-level overrides can be set with Set-SPOSite -ConditionalAccessPolicy AllowLimitedAccess or BlockAccess.
2. Block downloading of files detected as malicious
   • For files flagged by Safe Attachments in SharePoint, OneDrive, and Teams, users can be prevented from downloading them by running:

          Set-SPOTenant -DisallowInfectedFileDownload $true
     

These controls apply to SharePoint/OneDrive-backed content and to malicious files, but there is no documented setting in the provided material that targets inline images handled via Azure Media Services in Teams chats/channels or blocks their download specifically on unmanaged devices.

References:

• IT Admins - SharePoint and OneDrive unmanaged device access controls
• Safe Attachments for SharePoint, OneDrive, and Microsoft Teams
• Turn on Safe Attachments for SharePoint, OneDrive, and Microsoft Teams