Teams auto-updates when an update is available and the app is idle.
When an update is available in the Teams desktop app, it'll appear at the top of your Teams window. You can choose to update Teams instead of waiting for the auto-update during an idle period.
To update, select Update
> Update and restart Teams
.
Teams will automatically close and update. If it doesn't reopen automatically, select and open the updated Teams app on your device.
The web app is always updated. It’s just good like that.
Note
Linux users aren't able to update manually within Teams at this time.