After upgrading my main workstation to F30 a while ago (soon after it branched) dbus-broker failed to start, making my machine pretty-much unusable. I tried putting selinux in permissive mode and that fixed it, so I made a note to revisit this later.
Fast-forward to today, I applied all updates, did a full-relabel for good measure and things were still broken. Spinning up a fresh F30 vm does not exhibit this problem, so the problem had to be something specific to my machine. After lots of debugging I found bug 1663040 which is about the same thing happen on the live media and only on the live media, the problem turns out to be the selinux attributes on the mount-points (/dev, /proc, /sys) in / which cannot be updated by a relabel because at that time they already have a filesystem mounted on them.
I created the problem of the wrong labels myself when I moved from a hdd to a ssd and did a cp -pr of the non mount dirs and a straight forward mkdir to create the mount-points on the ssd. Zbigniew gives a need trick to detect this problem from a running system in bug 1663040:
sudo mount --bind / /tmp/foo
ls -lZd /tmp/foo/* | grep unlabeled
If the output of the last command show any files/dirs with unlabeled_t as type then your system has the same issue as mine had. To fix this boot from a livecd, mount your / on /mnt, cd into /mnt and then run:
chcon -t device_t dev
chcon -t home_root_t home
chcon -t root_t proc sys
chcon -t var_run_t run
Then umount /mnt and reboot. After this your system should be able to run in enforcing mode again without problems.