1. Remove Teams and install Teams Insiders

sudo apt purge teams && sudo apt install teams-insiders

2. Remove all Teams and Microsoft config files from ~./config and ~./cache

3. Edit /usr/bin/teams-insiders file by removing --disable-namespace-sandbox --disable-setuid-sandbox line

sudo nano /usr/bin/teams-insiders

… save and quit pressing Ctrl o and Ctrl x

4. Open the link via Firefox browser and choose xdg-open (MSTEAMS). Chrome based browsers dont open client window!