I took my own passport photo with my mirrorless camera, and a whiteboard as the background. It took a while to get it right, with no bright spots on the background and now shadows. It was accepted.
A tip for 10 years from now: take the picture with diffuse backlighting and you can easily blow out the background completely. For example, a sheer curtain in front of an outdoor window is just about perfect.
Ten years from now, hopefully you won’t have to be taking and printing your own passport photos. I haven’t done that in at least a decade, maybe two, in Europe. I go to the office that handles it and there’s a machine there that takes your photo.
The system here is simple, I just paid the 9,90 for photo, it is directly uploaded to the police and I am texted a code. I log on their system, put in the code. And pay. Passport is delivered to pickup location near me in week or so... Only issue is the signature and fingerprints, have to reserve time early or wait in line.