This milestone is to design and prototype an immutable version of postmarketOS. From a very high level we have the following requirements:

• A/B OTA mechanism with binary delta updates
• sysext/confext to provide dev tools and -dbg packages
• automatic rollback on failed updates

Long term goals (which affect our design constraints and should be decided on as part of this milestone, but don't need to be implemented)

• full verified boot chain on supported platforms (dm-verity)
• ephemeral /etc (can be wiped to reset system configuration back to defaults, initialised by systemd-tmpfiles)