2023-01-04, 18:14
Simplest way, but not free 
Since you already have an uSD adapter (I presume) to write images to uSD card, then you'll need additional eMMC Module Reader Board for OS upgrade
First use CoreElec (full) Backup option of present uSD card installation, and save it to an easily accessed secure location. Then with Balena Etcher burn new, same version, CE image (using eMMC Module to uSD adapter) on a PC. Remove uSD card from N2 and attach eMMC to install CE. After it boots and all is OK with new installation, restore previously made backup.
This way you'll get an exact eMMC system as is on uSD card.
Since you already have an uSD adapter (I presume) to write images to uSD card, then you'll need additional eMMC Module Reader Board for OS upgradeFirst use CoreElec (full) Backup option of present uSD card installation, and save it to an easily accessed secure location. Then with Balena Etcher burn new, same version, CE image (using eMMC Module to uSD adapter) on a PC. Remove uSD card from N2 and attach eMMC to install CE. After it boots and all is OK with new installation, restore previously made backup.
This way you'll get an exact eMMC system as is on uSD card.
