I've posted here before for the desktop view of my site. Right now, customizability has been very strong. I have no clue how to approach it on mobile, and I'm trying to take that seriously now that most of the development is over.

I set up a system where the background remains transparent IF a user has a background added. If not, it's just a white or a black background depending on the selected theme.

How can I go about text being readable, specifically at the top, while keeping in mind that every user has completely different backgrounds?

I attached two photos, one at the top of the page on mobile, another mid-way through the page, and the last one is just a desktop view. Half way through the page, readability isn't an issue, since text is bordered with boxes.

Is there a better way to approach the UI design for this? I'm lost.