If you have a scheduled Teams meeting already in your outlook calendar, you can join directly from the teams app without the outlook calendar (Outlook will not be installed locally so you cannot use outlook to join a teams meeting). You just need to add the calendar to the quick access bar in Teams.
If you do not see the calendar app in the Teams quick access bar on the left, Click the ‘…’ and then ‘add’ from the app menu. It should be first in the list, if not, search Calendar then click on it. See images below on next page.