A practical way to create, copy and paste LaTeX-generated equations in png format with transparent background?

In order of priority:

1. Online (I use Overleaf on a daily basis, Idk if it can help) (latex2png website seemed perfect at first but many packages are missing [e.g. I can't use the \mathscr{} command])
2. On an Android smartphone (with buttons for every symbol, typing backslashes on a phone is hell on Earth)
3. Locally on my computers (which is the option I like the less because I have to be using one of my computers)

After some research I found that the standalone documentclass was promising but so far I only managed to make it produce PDFs (or html files but is that even worth mentioning)...

Last note: if there really is no way to do that, I could cope with a white background.