UNOFFICIAL TIP :
if coming from an already installed “official” /e/OS and you want to upgrade to a15 “community” (without loosing data and locked bootloader)
- using → Settings → System updater → Local_update
- or using “recovery mode” and “adb sideload”
you will face a signature mismatch, simply choose “install anyway”
A clear guide to Upgrade your /e/OS to a new Android major version without loosing /data
Files for upgrading an existing /e/ system via local update or the /e/ recovery can be found here: