[General Questions and Answers] alecxs:
Google One looks pretty much like it offers that. This native bloat comes pre-installed on my device in /product/app/GoogleOne so I assume that is google's official backup feature provided for every android device.

Backup by Google One automatically saves data from your phone. This includes:

- App data

- Call history

- Contacts

- Settings

- SMS messages

- Pictures and videos

- MMS messages

You can check what data and which apps are included in your backup.

What else do you need that isn't covered by "App data"? full backup was possible from the earliest days, so I assume that behavior applies to cloud backup as well.

Not true. app is restored including app data, no need to setup from scratch. except for apps where the app developers made decision for. this is not a limitation in design, it's a feature for app developers to deny access to app data. in your opinion this feature is useless, but app developers have different view on things.

Besides granting permissions again, what "lot of work" is it exactly you mean here? Again, this is a feature not a limitation. not restoring permissions is for security. Do you realize that apps lose it's permissions intentionally if unused?

https://9to5google.com/2021/09/17/android-unused-apps-permissions

So let's have a look into risk of allowing backup app data if we provide a backup solution that includes these things, ignoring app developers decision.

https://digitalforensicforest.com/2016/01/28/android-backup-file-ab-analysis

So let's give you example. Few years back (before corona lockdowns) I used app com.limebike. This app also has employee mode with login secured area called "Juicer mode" intended for collecting e-Scooter for maintenance or charging. To get approval for registration user must have business licence, so I have signed up contract as freelancer. each user must be adult and have its own registered account. If you login into one device, all other devices will be logged out automatically. This is realized by additional login credentials (device unique ID) stored in app data.

Stupidly enough, app developers have set android:allowBackup="true" accidentially (it's a cloud-based app all data is saved on server bonded to user account, so there is no need to backup anything btw) so I was able to access app data by simply typing adb backup com.limebike which makes 1:1 copy of secret login credentials. I was able to adb restore backup.ab to other android device (without root) and - voilà - both devices were logged in simultaniously ("Two Juicers are better than one")

In Juicer mode a "Juicer" can unlock the scooter for 24 hours for collection. So guess what? I sent backup.ab to all my friends (and even my minor son) and they were able to unlock scooters and ride for free! Even better, I gave them chargers, so whenever one of my friends decided to take a free ride, I earned money!

I think thats 'good reason' for app developer to opt out of data backup, don't you agree?

I am sure there are plenty much apps where access to app data is forbidden for reason. I don't use banking apps, crypto wallets, amazon or netflix personally, neither I am app developer so I can't say if there better methods to protect app data, but one thing all cheats have in common they depend on security vulvnerabilities and app data leaks. (If you're playing games on your mobile you probably know about Lucky Patcher)

Now, imagine you're the app developer of com.limebike and want to close this backdoor by checking SafetyNet and changing android:allowBackup="false". What do you think, would you still provide your app in Google Play if android says "Hey, we don't care about your security, let users backup their data anyway"?

So in your opinion Android has a big limitation in the way it is designed, but in fact that's not a technical limitation but a feature.