The instructions at Boot from a MicroSD Card | Mixtile require running a Windows utility in order to create and write an image to MicroSD - how can this be done from a Linux host (… preferably, another Blade 3!)
Where are the technical details of exactly what actions the utility is taking and what partition scheme or data it’s actually writing?
From reading Firmware Images | Mixtile, would I be correct in saying that raw firmware images can be written to a MicroSD card normally (e.g. simply dd it across?) and will just work without needing any special tool?
It’s correct. You can write raw images directly to your MicroSD card using normal tools like balenaEtcher (https://etcher.balena.io/).
However, Rockchip format images require a specific tool that’s not currently available for Linux users. Unfortunately, Rockchip hasn’t released that tool for Linux yet.