mendymishmn A few points:
mendymishmn I think that people can download inappropriate content to their phone the same way they would have downloaded apks to their phone. Somebody with a kosher phone, kosher computer, kosher tablet, cannot download inappropriate content onto his phone.
All the Roms have different settings. For example, some have no video. Yes, some inappropriate content can be downloaded onto the phone (assuming one has access to a device to download that content). But, if you make a phone kosher, that means it shouldn't be able to download such things.
Being able to install any app you want includes social media, streaming sites, youtube, dating apps, and even Browsers. That isn't called kosher. It would defeat the purpose.
mendymishmn I also think that someone who is kashering his phone is in a strong, healthy place at that time, and will choose the ROM with the kashrus standard appropriate for him. If he knows that he can't handle himself with a ROM that allows apk installation, he'll get one of the higher standard ones.
But if you are allowing APK installation, you are not kashering your phone! You may as well keep the browser.
mendymishmn If he's not bichlal interested in kashering his phone, than he already has a browser from the beginning. Who is being saved?
And if he is interested... then why should he allow APK Installation? I would ask the opposite question:
If a guy isn't interested in filtering his phone, he wont install a filter anyway. If he is interested, then he'll block APK installation. So who would a rom with APK installation be for?