Hi @l0194l
Although some networks and countries actively choose to have the bootloader locked, we don't usually ask this for our stock, so it would be down to the individual manufacturer how they choose to ship their devices.
That said, my Android phone from EE (of a different brand) is not OEM locked- I have the slider which I can switch on and off.
We can't guarantee the OEM unlocked option will be in the developer settings, but we do advise against making changes that could make your device potentially unsecure. Although, as you're asking the question, I'll assume you'll already be fully aware of the risks of changing the device firmware!
Hope this helps!
Ali
