A lot of the apps these days are built either with React native or NDK. The former is for web like apps, the latter is for performant apps.

Other than the fact that an android app to has to bundle every dependency, Facebook apps also have lots of "useless" features.

For example, Messenger can show you how many Facebook notifications you have (only necessary because Meta doesn't know how to send an actual notification half the time). It also has "Stories", some "AI Studio chats" and a "Create an AI" button???

Also, I think they also have the ability to update themselves, because Meta doesn't trust google play?

And let's not talk about the main FB app bundling an entire web browser, which recently is your only option when clicking a link in Facebook.

Apks are zip files. If you pull the apk, load it a tool and see what's there. One exciting thing is the typical way to do string localization in Android results in the string resource files being in the zip file uncompressed. If your apk supports a lot of languages, that's a lot of space. FB Messenger shouldn't have a lot of uncompressed strings, they had a way to manage that when I was there (left 2019), and I think??? there is some support from Google to do better things now too. But between that and images for multiple dpis (which does also have some Google support for doing better), there's a lot of room for bloat. If you're getting a non abi specific apk, there's bloat from different binary libraries too.

FB in particular likes to have multiple ways to do the same thing, which sometimes means having libraries to do X from JVM as well as doing X from native code.

> OS, drivers and libraries for (3D) graphics up and running Right, except that I am not saying one should build a kernel, and webgl, cuda, etc are kernel dependant not OS dependant

> assurance that you still can get hardware to deploy your stuff on X years from now I am unaware of android-specific hardware features to date (linux specific, maybe, but not android) -- you can literally add any bootloader and load a linux kernel and get drivers running on most phones even, w/o android, and where "android" is necessary it's simply an artifact of the company maintaining the phone having build the drivers into their distro and not released them separately.

> You also don’t want to order a million units up front. Again, seems unrelated, I'm talking about building the VR hardware i.e. not order off the shelf and white label (unless your claim here is that meta, htc, steam etc are doing white labeling, which doesn't seem to be the case)

Executables, daemons, CLI, sockets, whatever you want. Rust no problem. I have even run Python and Node.js