Icons are in /usr/share/icons, but I can't apply them

[Moltke]

Moltke, when I enter the command with no "s" at the end of cache, like:

sudo update-icon-cache /usr/share/icons/*

Terminal says "command not found". I've also tried the other command you mentioned ("sudo gtk-update-icon-cache /home/your_user/.icons/Icon-Theme-Name") and Terminal returns "no theme index file".

Short of installing via another means (i wonder if there's a .deb file for that icon set), I don't see what else I can do. I like the Arc icons, but I like Paper better.

You did change "your_user" and "Icon-Theme-Name" by the actual thing, didn't you?

Sometimes, it's as simple as visiting the author's webpage (https://snwh.org/paper/download) and download/install from there following instructions (in my case, by adding the ppa then installing from that source)...

*fullsize "facepalm emoji"*

Yeah, sometimes you have to go to the source itself. You might want to heck here https://www.xfce-look.org/browse/cat/ Glad you solved it!