steamos-readonly

The Steam Deck comes configured in a way that part of the filesystem is set to readonly mode. This sometimes gets in the way when installing custom things on the desktop mode. Like when installing the great Starship prompt.

You can disable the readonly mode with:

sudo steamos-readonly disable

and re-enable it with:

sudo steamos-readonly enable

It's not very well documented what parts it actually protects and this command is not very much documented anywhere either.