From my understanding, you just have to wait the 24 hours once to allow 3rd part apks. You don't have to do it for every app install.

You can get hdmi cec working. It just requires some tinkering at the moment. I do see valve improving it for custom builds though.

https://addons.mozilla.org/en-US/firefox/addon/yesterday-for-old-reddit/

Use that instead. Makes old reddit more mobile friendly. Though I did have to turn off some settings because they were laggy.