Is it possible to do this or is it controlled by Toshiba?

It's controlled by the manufacturer, they really aren't particularly 'smart'.

I bought a Toshiba set early this year and returned it the next day, as you could load hardly anything onto it - not even the Google Chrome browser.

You can't add anything of your choosing, it is not a PC.

You get Firmware updates from Toshiba that 'might' add an App/Service/content.

The provision of those is by Toshiba plus the other App/Service/content supplier.