Lost my OS during factory reset

[piero]

If you have recovery-e instead if TWRP,
You can choose “apply update from SDcard”

[HOWTO] use e-Recovery to wipe & format data before sideloading/install eOS

This HowTo doesn’t apply to your device if the installation instructions for your device don’t mention a recovery. For example the Fairphone 3. The e-recovery.img will perform many of the same functions as twrp and is probably a bit easier in some respects for installing the eOS.zip. There are just a few basic steps to carry out: select Factory Reset, then Format data / factory reset and continue with the formatting process Return to Home Screen Select Apply Update, then Apply from ADB …