personally, I use webdav; however there are a lot of good reviews of seafile if you want a true replacement of owncloud.

unless, of course, you care about security or a project that is, well, alive... There have been 1 or 2 commits in the last month so I wouldn't bet my data on it.

But I'm hopelessly biassed, working for Nextcloud, so please check github for yourself when you pick a solution for your data - at least look at the pulse over the last week or month before you pick a solution. If you don't know it, here is ours: https://github.com/nextcloud/server/pulse it shows you the activity in the project. For comparison, this is bad: https://github.com/haiwen/seafile/pulse

Again, I'm biassed, so make your own conclusion, don't rely on mine. I'm just pointing the way.