I've bought a USB flash stick with a write-protect switch. I've installed and updated buster and enabled the overlay fs (also changing /boot to read-only).
The intent is to be able to boot with the WP switch on, do whatever I want to do, and then power off and reboot with no changes made to the underlying fs. However, when I attempt to boot that way I get thrown into an emergency shell (which fails because root is locked) because fsck fails because the media is read-only.
What I really want is to be able to boot with the WP switch off when I want to make permanent updates and the like, but then boot with WP turned on when I don't want the state altered.