How did you get to this point? Looks like an update failed and the phone now has a corrupt bootloader. I'd advise contacting support Product Help & Support | Samsung UK or via socials @SamsungUK, as your phone may need to be re-flashed. I'd say it's worth reaching out and going over some troubleshooting steps though. Nothing I found seems appropriate for this, if holding the power button does nothing.
If it was my phone, I'd be keen to see what happens after the battery dies, in terms of booting. Could just bring the same message though.
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