You can install strongSwan and use LimeVPN on your Android TV. Follow the instructions below.
1. On your Android TV, open the Settings menu.
2. Inside the Settings menu, go to Personal -> Security and Restrictions
3. Enable the UNKNOWN SOURCES option.
4. Install Sideload Launcher - Android TV from Google Playstore (Link). This app will help you sideload apps that are not in Android TV Playstore.
5. Install ES File Explorer from Google Playstore using the link here. If you already using any other File manager with cloud support, you can continue with that.
7. Upload it to either Google Drive or Dropbox.
8. Open ES File Explorer and from the left menu, select Cloud.
9. Link your Google Drive.
10. Select the Drive and select the file.
11. From the options, you can install strongSwan.
12. Now open Sideload Launcher where you can see the sideload app strongSwan.