the popularity is deserved as there exist adjacent apps and community forums for help. The minimal chat/webrtc solution "Talk" is great for family and friends, the (Android) Talk App itself made leaps last year. It will also write plaintext rows per chatline to the db, but that's okay. Things transferred via webdav can be clientside encrypted, cal- and carddav again is cleartext. Etesync can do it encrypted but then you'd leave the all-in-one package. It's even more fun with customroms having davx and a webdav sync solution already integrated.