How to Turn On Dark Mode Everywhere on Android (Including Apps That Don’t Support It)
System dark mode plus the hidden force-dark developer option that covers apps without a dark theme, caveats included.
Display
How to Make Your Phone Easier to Read (Text Size, Contrast, and More)
Font size is only one of Android’s readability settings. Here is the full stack (display size, bold text, contrast, magnification) and the trade-offs.