Comment 6 for bug 1873520

Closing as won't fix: the serial console is too important to disable by default on our server images, and there's nothing we can realistically do about a piece of hardware that attached to the serial pins that spams the serial console as a result (u-boot *should* be interruptible by key-press after all).

This is *less* of an issue in 22.04 as u-boot is not in the boot sequence there, but the boot screen will still flicker on that release as plymouth perceives the escape key being repeatedly pressed on the serial console, so the work-around still applies there (change enable_uart to 0 in config.txt).