But isn't it quite useless to backup WA when it's all encrypted and you can't backup the key?
Nowayadays Syncthing is no more maintained due to some PlayStore drama, but Syncthing-Fork is a good replacement.
There seems to be an issue with recent Android apis that make file access painfully slow that it wasn't able to sync my data in 1 full day. Enabling the "Case Sensitive FS" option on the folder helped a lot.
https://github.com/Catfriend1/syncthing-android/issues/1088#...