Just remove splash=xxx and quiet boot options at GRUB. e.g. press 'e' to start editing mode on GRUB, drop those options from "linuxefi" or "linux" line, then continue to boot with ctrl-X. And, try to trigger the reboot with ctrl-alt-del. You might need to trigger (quickly) multiple times to let systemd forcibly reboot, but it's better than the hard switch off by the power button.