A phone camera is more than good enough. The setup matters more than the hardware.
Find the right wall and light
A plain, light-coloured wall with a window to one side. Turn off overhead lights. Stand about half a metre from the wall so no shadow lands behind you.
Get the distance right
Have someone hold the phone at your eye level, roughly an arm and a half away, and use the rear camera — the front camera distorts facial proportions at close range.
Do not use portrait mode
The artificial background blur is a form of editing and will be rejected. Use the standard photo mode.
Frame loose, crop later
Leave room around your head and shoulders. It is always easier to crop in than to invent missing pixels.
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