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So as far as I can tell, so far everyone who has checked has the broken out of date System RecoveryOS install after a Sonoma upgrade.
This means that all MacBook 14" and 16" users have unusable System Recovery if their display settings are not ProMotion, and many with older versions probably have broken recovery outright for being too old.
This is really, really fucked up. How on Earth did Apple screw this up this badly.
More info: https://github.com/AsahiLinux/docs/wiki/macOS-Sonoma-Boot-Failures