I can’t seem to understand this. Seafile is a serious general file synchronization tool with class-leading security and performance. Why does the Android app limit itself to photos and videos? It’s so off-brand. Is seafile an aspiring social network or a serious file synchronization tool? Others have been made to wonder the same: Android App: Uploading PDF from download folder? - #3 by Mark_Y_Mark.
I genuinely would like to know - why the decision to limit the android client to media only?
I would like to understand this too.
Why can we not sync, for example, WhatsApp/Signal chat backups?
Why not just allow syncing any files?
Are WhatsApp/Signal chats stored as files under a folder?
Yes daily backups are kept in internal storage for Signal and WhatsApp.
In Signal settings you choose which folder on the device you want them to be stored in. It keeps the most recent two and deletes any older when it makes a new backup. Files look like signal-2022-08-31-23-19-09.backup.
For WhatsApp, they are stored in:
Android/media/com.whatsapp/WhatsApp which contains 3 sub-folders, Backups, Databases and Media.
The chat histories for each day are stored as archives in Databases like this:
msgstore-2022-08-27.1.db.crypt14
Hi @daniel.pan are there any plans to allow synchronisation of other directories or file types?
We are working on this feature “back up any folder in the mobile”.
Why not 2-way sync? 
I don’t get why none of the cloud storage services allow for 2-way sync and I have to use SyncThing or AutoSync instead. If it can be done by third party tools, why not implement the feature within the cloud service app?
@daniel.pan thank you, is this just one-way sync, or two-way?
As SolarDesalination says, presumably there is nothing to prevent the synchronisation happening in both directions, as with SyncThing and similar apps?
It will be one-way sync (backup).