How to permanently uninstall Microsoft Teams?

Because the Linux version of the Teams application is supplied as a .deb file, the installation is registered in your package management. You can remove the application using sudo apt remove <packagename>. To learn the precise name of the package, inspect the list of installed packages using the terminal (you can use "grep" to filter on e.g. "teams") or using Synaptic Package manager (not installed by default) (where you can search).

Note, however, that as part of the installation process, Microsoft also added a software source (PPA) for Teams. That ensures that you automatically receive updates. After removing the Teams software, you may also wish to disable or remove that PPA (packages.microsoft.com/repos/ms-teams) in "Software & Updates", tab "Other Software".