Reduce install instruction for Debian

README.md

@@ -60,17 +60,13 @@ On OS X you can use [Homebrew](https://brew.sh/) to install the app.
 brew cask install copyq
 ```
 
-### Debian and its derivatives
+### Debian 10+, Ubuntu 18.04+, and their derivatives
 
-Users of Debian unstable, Debian 10+, Ubuntu 18.04+ and later derivatives can
-install stable version of copyq from their distribution's official repository:
+Install `copyq` package.
 
-```bash
-sudo apt install copyq
-# copyq-plugins and copyq-doc is splitted out and can be installed independently
-```
+`copyq-plugins` is highly recommended. `copyq-doc` available.
 
-### Ubuntu PPA
+#### Ubuntu PPA
 
 Install and keep CopyQ always up to date by running the following three commands from the terminal: