This tool is for exporting Microsoft teams chat data from any user of the organization, with a pst file. The admin who will be connecting to powershell must have the eDiscovery Manager and Compliance administrator permissions assigned.
For users hosted onprem keep in mind that if you have never performed a search for a onpremises mailbox you will need to read this article https://docs.microsoft.com/en-us/microsoft-365/compliance/search-cloud-based-mailboxes-for-on-premises-users?view=o365-worldwide
Now search for onpremises mailbox is aviliable WW for all tenants!
Download the PS1 file and open powershell as an admin
.\TeamsExportChatTool.ps1