I was rather surprised by this too. When the UI changed I was already a
bit sceptical as KeePassX has not changed in like five years. When it
did not open the old database I knew that I was served version 2. A
short look in the dnf automatic update emails confirmed that.
The mid-release break was unexpected. I have converted my database now
and kept the old one. As there is nothing wrong with 2.0 and most of my
devices are the same Fedora 23, I will be able to work with the new
database.
I have thought that the version 2.0 would come eventually, just not
mid-release. So even if there would be a package for the old version, I
would not go back as the new one seems to work just as well.