Being curious. What is "a variety of conflict issues"? Also could you perhaps expand on "the client had some problems"? Which client? I know an official Windows client exists as well as an Android client (this latter I use), but all communications are via HTTP (DAV for file transfers / calendar / etc. & REST for admin stuff), which means that a specific client is not necessary.

Personally, I use KDE's file manager (Dolphin). Plus a curl-cased Bash script for when I need to upload an arbitrary file from one of my home computers via my phone (SSH from phone to computer, sometimes over sat link, run "~/bin/upload.sh /some/file").

I manage my own ownCloud servers (one personal, one company), but hosted options are available.

And yes, it does keep file history (optional, enabled by default), as well as encrypted storage (optional, disabled by default).

Neither the client, nor the server even, require any administrative access.

I had couple conflicts in the few years Ive used it, but they were few and were actual conflicts (a file on a client was updated at the same time the server copy was updated). It does keep a limited file history. I'm not really using it for file history so I'm not sure exactly what the rules are for retaining old versions.