I have the same issue
I'm on KDE Neon 5.23, Kernel 5.11.0.38-generic, Nvidia 470.74, X.org 1.20.11, X Protocol 11.0
I can't connect the monitor before the first login, otherwise the UI freezes and fans ramp up a little, same issue happens if I disconnect the monitor with the laptop on.
The only way to recover from these freezes is to force a power off by holding the power button
Logs attached
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