It isn't firmware, it's an OS/ROM. If you still have stock Android installed, you might be able to use DSU loader which can be found in Developer settings.were can i find that firm wear at thanks i diff well give that one a try
GSI = No Google installed
GSI + GMS = Google installed
If you don't have Android installed then go here: https://developer.android.com/topic/generic-system-image/releases