What's a good website to find app icons?

Is there a one-stop shop website for app icons? Please share if you know of one. Thanks in advance.

Well, it’s not one website but Wikipedia or the git repo of the project is generally the best place to find one. And if you want icons to use in text, checkout NerdFonts or Font awesome

Are you looking for app icons for your computer, or are you a designer and want app icons for your designs?

If for your device, I’d say just install the Tela Icons pack. They are the most complete IMHO, and they look nice too.
https://www.gnome-look.org/browse?cat=132&ord=rating ← For GTK
https://store.kde.org/browse?cat=132&ord=rating ← For Qt

If for designs, you got many options. Here are some:

I am creating custom app icons via KDE menu editor and assigning graphics to them for placement in my plank dock. Just want some nice icons that look modern and polished, with a large library to choose from. I’ll check these out.

Yeah, so the KDE/Gnome stores would have pretty much everything you need then. And as I said, the Tela Icon pack has many icons to choose from