Hello, I use Chrome's devtools to test CSS on mobile devices. Here's how:
Opening Fandom on Mobile:
Press F12 (or right-click -> Inspect Element).
Click the "Toggle device toolbar" button at the top-left corner of the DevTools UI (or CTRL + Shift + M).
Reload the page to load Fandom on mobile.
Adding custom CSS style rules:
Click on the "+" icon that's a little bit to the right and down the center of DevTools ui. A new "style rule" will added below.
Click on "inspector-stylesheet:1" that's to the right of the style rule.
Congratulations! You can now test custom CSS on mobile!
I don't think I ever once needed to use PortableCSSPad; I always just used DevTools.
Learn more about DevTools: https://www.youtube.com/watch?v=t1c5tNPpXjs
Edit: On another note, I am quite surprised to see that my response was apparently "100% ai-generated" according to Quillbot. I literally typed it myself................................................................................................................................................................................................................................................................................