Is it possible to merge or split APK files into one or install split APK files, on Android device itself, without root?

Background

In the past, I've asked about sharing or backup of app-bundle / split apk files, here .

This seems like an almost impossible task, which I could only figure out how to install the split APK files, and even then it's only via adb:

adb install-multiple apk1 apk2 ...

The problem

I was told that it should be actually possible to merge multiple split APK files into one that I could install (here), but wasn't given of how to do it.

This could be useful for saving it for later (backup), and because currently there is no way to install split-apk files within the device.

In fact, this is such a major issue, that I don't know of any backup app that can handle split APK files (app bundle), and this include Titanium app.

What I've found

I took a sample app that uses app-bundles, called "AirBnb".

Looking at the files it has, those are what the Play Store decided to download:

So I tried to enter each. The "base" is the main one, so I skipped it to look at the others. To me it seems that all have these files within:

• "META-INF"
• "resources.arsc"
• "AndroidManifest.xml"
• in the case of the one with the "xxxhdpi", I also get "res" folder.

Thing is, since those all exist in multiple places, I don't get how could I merge them.

The questions

1. What is the way to merge those all into one APK file?

2. Is it possible to install split APK files without root and without PC ? This was possible in the past on backup apps such as Titanium, but only on normal APK files, and not app bundle (split apk).

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EDIT: I've set a bounty. Please, if you know of a solution, show it. Show something that you've tested to work. Either of merging split APK files, or installing them , all without root and right on the device.

from Is it possible to merge or split APK files into one or install split APK files, on Android device itself, without root?