Solution for Microsoft Teams is available since RSS Reader Web Part version 188.8.131.52.
- Open the Team on Teams panel that you intend to add the Web Part;
- Click on the [+] button to add a new Tab to the Team;
- On the Search type RSS Reader and select the BindTuning RSS Reader
- It'll open a modal where you can post that you've added a new tab or not. After selecting either or not to post, click on Save.
- The tab will be added to the team.
Now the only thing left to do is to connect the web part and setup the rest of the Web Part Properties.