Cant access to « Install from unknown sources » on Xstream tv

Hey folks, I recently got the latest Airtel Xstream IPTV box (running Android TV), but I’ve hit a wall trying to sideload apps. The option to "Install from Unknown Sources" is completely missing or greyed out in the settings. I've checked under both Security and Apps > Special Access, but no luck.

Has anyone else faced this issue? Is there any workaround to enable sideloading?

Would appreciate any tips or step-by-step if you’ve managed to get around this!

Thanks in advance.