Officially only devices of the hardware supporters. Mainly Khadas Vim3(L), Minix and Beelink.
The official way to go is the ceemmc tool. More Infos here: How to use the Team CoreELEC ceemmc tool
Unofficially, almost every next-gen device out there. You need the -x switch.
Worked flawlessly in dual boot mode (CoreElec and Android on emmc) with my Bqeel Y8 max, which is discontinued.