Won't boot (prohibited sign with support URL) after changing serial

Context: My serial got banned after using beeper mini. I am on a real legacy Mac, not a hackintosh. I generated a new serial in the opencore app, and selected spoof 'minimum' to see if just changing the board serial would be enough to unban me.

I didn't change anything else about my configuration.

After rebooting, I get the prohibited logo and the apple support link.

How can I recover from this situation?

submitted by /u/pricklypolyglot
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