The app ecosystem
This is the single biggest reason Android wins. The mainstream OTT apps — Netflix, YouTube, Disney+, Prime — are built as Android apps and run on the Android app ecosystem. A Linux box can't run them at all; adding a third-party app there is a bespoke integration that, for most operators, isn't worth it. If a subscriber's first question is ‘does it have Netflix?’, Android is your answer. If you deliver a closed IPTV bouquet and OTT apps aren't part of the deal, this disadvantage simply doesn't apply to you.