Timmy T beat me to it: you need a minimum Android 7 bootloader to install latest CE on emmc.
If you want to upgrade you will loose some add-ons (python 3 migration) - maybe they were ported already. Just drop a tar of CE 19 in the update folder and reboot. My advice would be to get a backup of Kodi settings and restore it after you perform a factory reset after the upgrade. You also could upgrade by choosing the update channels.
I would perform a fresh install - How to use the Team CoreELEC ceemmc tool and restore the old settings.