Importing messages into MS Teams:

https://docs.microsoft.com/en-us/microsoftteams/platform/graph-api/import-messages/import-external-messages-to-teams

https://developer.microsoft.com/en-us/microsoft-teams/blogs/importing-3rd-party-platform-messages-to-microsoft-teams-is-now-available-in-beta/

Unofficial client for teams v2 as Microsoft discontinued Teams v1 and are not releasing an official linux client any longer:

sudo mkdir -p /etc/apt/keyrings
sudo wget -qO /etc/apt/keyrings/teams-for-linux.asc https://repo.teamsforlinux.de/teams-for-linux.asc
sh -c 'echo "Types: deb\nURIs: https://repo.teamsforlinux.de/debian/\nSuites: stable\nComponents: main\nSigned-By: /etc/apt/keyrings/teams-for-linux.asc\nArchitectures: amd64" | sudo tee /etc/apt/sources.list.d/teams-for-linux-packages.sources'
sudo apt update && sudo apt install teams-for-linux

For login issues with apps, use CTRL+Click on link to sign in. This may not always work

To add/use teams4linux as application for msteams urls, use:

xdg-settings set default-url-scheme-handler msteams teams-for-linux.desktop

Check in FF/TB/Chrome application to ensure it's set to use Teams4Linux.