How to "fastboot flashing unlock" when device has no volume rocker?
When a device has no volume rocker it is usually flashed using an external tool and not via traditional fastboot methods.
In this case, the device is a MediaTek Android smartphone (MTK based), and nearly every smartphone with this chipset can be flashed not using fastboot, but with the SP Flash Tool.
The latest version SPFlash Tool v5.1924 can be downloaded at:
spflashtool.com or androidmtk.com
This tool allows the flashing of Scatter Based Stock Firmware on devices powered by Mediatek Chipsets. All you need is the correct Scatter based Stock Firmware of your Device.