I just downgraded systemd to 226-4 for similar reasons. After boot the root file system was mounted read-only. I logged in and remounted it to read-write and it looked right at first. But after I logged out and in again it was again mounted ro. The next odd thing was: after remounting it to rw I tried to login on X (sddm- greater) and failed immediately.
I found this bug report and gave it a try - downgrade systemd to 226-4 and everything is back to normal. I have to do some work now and have no time to investigate this further, but the problem is real... My file systems are all ext4 - so ZFS is not in scope for me. Cheers, Stefan
