Probably not really, as filesystem root has circular virtual filesystems which are not supposed to be synced. So you’d spend tons of time ignoring random things to get it to work. Also, even if yoy achieved that, I am not sure if this was usable for recovery purposes.
Make sure, you do NOT sync any databases or log files which are in permanent change by apps. That’s why I’ve excluded WhatsApp’s DB folders. They may raise conflicts, pull errors, battery drain because of errors and so on.
Make sure, you do NOT sync the /Android folder. I’ve tried syncing it some years ago and ended up putting new sub-folder ignores every week which wasn’t easy to maintain. From my experience: Very little kind of apps keep their data on /storage/emulated/Android/0 in a use-able form. For me, it was OSMAnd, for example, keeping map material downloaded from OSMAnd servers.
Like Audrius said: On the one hand you can get a pretty good backup of your USER data which means FILES (e.g. photos, videos, music, recordings, manually to-file-exported app settings, etc.), but due to Android restrictions you can NOT get a use-able backup of your app settings, internal files an app has downloaded on /data/ partition (…). I’ve tried this in my root days and had just a large bunch of useless files on my NAS hogging up my phones sync performance on the other side without any benefit when I had to recover my phone.
Long story short: Try to ONLY sync your USER files from /storage/emulated/0 without special folders (/Android), logs (/Tasker/logs/*), databases (/WhatsApp).
I hope it helps you a bit.
And yes, Android has in my eyes proven not to be a long-term “stable” platform for Syncthing as OS changes often offend the app to even exist (see Android 10 scoped storage, for example, which will finally hit Syncthing in Android 11 according to Google’s nowadays announcements). That’s why your NAS is recommended to have a backup mechanism in place to BACKUP your synced data which came from the phone. Android glitches (coming with an Android upgrade) could cause Syncthing to fail - Syncthing cannot be held responsible for this and is a SYNC solution, so a good BACKUP on the nas side, e.g. copying snapshots of it to an external hard drive every night like I do, is advised.
Unfortunately that’s really bad news for me. I’ve been syncing USER FILES on my Androids already. What I’m trying to achieve now is a backup that goes beyond that, including app settings and internal /data/. I hoped to go beyond the limitations of oandbackup by handling the files directly.
Is it really impossible to build backups close to the iPhone/iTunes ones where you get EVERYTHING?
Since modern android is much more than ‘just files’, the best way to go would be to create a full system backup using an application made for the task (e.g TWRP recovery, Titanium Backup) and sync the file(s) created by the application.
Directly accessing internal filesystems, databases and stuff is something that I wouldn’t recommend to anyone, especially since Android nowadays involves multiple layers of encryption and access protection. I’ve once attempted to copy over a few app databases from phone A to B, some of them worked others just crashed the apps. Full system backups created by a specialized application should work best.
Hmmm what works good if you are a techy might be AdeBar from izzysoft (github). It’s a script that can backup apps and settings pretty well using adb. The unlucky alternative would be Google Drive Backup (Honestly I dont like it, technically it works).
Yeah, that’s what I do at the moment using oandbackup (open source). But it has its limitations (messaging apps like Signal or Threema can’t be restored). And a TWRP backup can’t be automated and done live and restored partially.
I’ll check out AdeBar, thanks! Google’s not an option, I’ll never install Google Services or anything from them.