I experienced a similar issue when I installed 12.0.1 today on my MBP 16 that's about 18 months old. The refresh rate in the display settings on the computer defaulted to 30 MHz. I changed them to 60 MHz and it fixed the issue.
I have 2x LG 27UL650 displays. My system would freeze on shutdown, restart, sleep, lock, etc. I entered recovery mode and reinstalled the OS. Same result. Updated the LG drivers. Same result. I reset NVRAM. Same result. My system booted, restarted, and slept fine without the monitors connected. Then I read about the issue here. I reconnected one monitor, set the refresh rate, and the system restarted normally. I repeated the process with the second monitor.
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