I hit an issue with Fedora 43 recently on my Framework laptop. After a reboot the machine was stuck at a loading screen indefinitely.

Pressing Esc I was able to see some helpful log entries. 

...
systemd[1]: Unable to fix SELinux security context of /dev/tty37: Permission denied
systemd[1]: Unable to fix SELinux security context of /dev/tty38: Permission denied
systemd[1]: Unable to fix SELinux security context of /dev/tty39: Permission denied
...
systemd[1]: Too many messages being logged to kmsg. Ignoring
...
...;type=boot[!!!!!!] Failed to allocate manager object.

I was only able to boot to a meaningful state by editing the GRUB boot entry and adding selinux=0 to the boot command line. With that temporary workaround I could boot into Fedora.

Google AI results then suggested a series of commands that resolved my issue.

Create a trigger file in the root (/) of the filesystem to cause a filesystem relabel. Interestingly, this file already existed on my machine. I’m assuming something went wrong with a past Fedora upgrade on my machine so that this file was created, but the relabeling did not succeed. 

sudo touch /.autorelabel

Update the SELinux config file.

sudo nano /etc/selinux/config

Change the line with SELINUX=enforcing to SELINUX=permissive. This allows the machine to perform the relabel on the next reboot.

Reboot and do not hack the GRUB boot entry as before. Instead, boot as normal. Pressing Esc while the system boots shows some new progress. 

...
selinux-autorelabel[1486]: *** Warning -- SELinux targeted policy relabel is required.
selinux-autorelabel[1486]: *** Relabeling could take a very long time, depending on file
selinux-autorelabel[1486]: *** system size and speed of hard drives.
...
selinux-autorelabel[1464]: Relabeling / /boot /dev /dev/hugepages /dev/mqueue /dev/pts /dev/shm /home /run /sys /sys/fs/cgroup /sys/fs/pstore /sys/kernel/debug /sys/kernel/tracign /tmp
...

Eventually the system should boot normally.

We can now restore the original settings in /etc/selinux/config and set SELINUX=enforcing.

At this point my system was able to reboot again normally.