I am pretty content with my Linux Mint (19.3) setup with the Cinnamon DE. Since Linux Mint is based on Ubuntu, I'm pretty confident that any solution you come up with, will work on Linux Mint as well.
I have one annoyance: I use Notepadqq on a daily basis. It seems that Notepadqq does not adhere to the icon theme I chose.
I installed Notepad through its default PPA (Notepadqq : “Notepadqq Team” team), not with snap.
I have chosen a dark desktop theme (vimix-dark-laptop-doder). The icon theme I chose (Vimix-Ruby-dark) contrasts well with the dark theme. Well, everywhere except in Notepadqq. Here's an example
Screenshot of my Notepadqq toolbar:
So, my question is: how can I change the Notepadqq icon theme - or its individual toolbar icons - without changing the general icon theme?