Interesting. I saw the Beeline Reader before and their method is different in a way that doesn't negatively impact my reading. Their grayscale palette is actually fun and unobtrusive enough that I forget it exists after a while.

Also, their text is left-aligned.

If you're up for more experiments, try a line highlighter that follows a cursor, like so: https://blog.adobe.com/en/publish/2021/05/06/hacking-readabi...