At the GRUB menu, edit the first boot entry. Remove rhgb quiet and add rd.shell rd.timeout=30 systemd.debug-shell=1 3
Depending on what’s wrong, you might get to an emergency shell, login prompt, or hang. If hang, try to switch to tty9. There should be a debug shell there, root user, no password required. Otherwise login.
Plug in a USB stick, mount it somewhere, and save it the journal to the stick.
journalctl -b -o short-monotonic > /path/to/file.txt
Unmount. Attach that file.