Teams Chats backup is currently using Microsoft Graph API calls that are still in BETA. More information here.
Altaro Office 365 Backup has the ability of backing up Microsoft Teams Chats (Users and Groups). You can find a full list of what is included in backup here:
Manual backups
It's important to note that when triggering a manual backup from the context menu by click [Take Backup], all chats for the entire tenant are backed up seeing that chats are stored at a tenant-level rather than at a user-level by Microsoft.
Licensing
Teams Chats backup is supported only with a '365 Total Backup Subscription' plan.
Limitations
- Reactions on messages are not backed up and restored
- Files sent over chats will be backed up first time round, if the file is later modified via OneDrive and not resent on the Teams chat this will not be detected during the chat backup. This will however be backed up via the OneDrive/SharePoint backup.
We can only detect that a new user has been added to a chat if there are changes in the Teams Chat since it’s last backup
Only Display name can be backed up for Tags used within Group Teams channels
All chat messages that form part of an ongoing Teams conversation will be included in a user's backup, including messages posted before the user was added to the conversation, regardless of the share options selected while adding the user
Private Group Conversations are skipped if the group has been deleted before the first backup of that group teams chat took place
Files shared by an external user are not backed up
Saved messages are not backed up
For more information on features supported for backup you can visit this article.