README: provide the Focal PPA

README.md

@@ -32,7 +32,13 @@ contain many small C and C++ programs respectively. `notcurses-demo` covers
 most of the functionality of Notcurses.
 
 **If you're running Notcurses applications in a Docker, please consult
-"[Environment notes](#environment-notes)" below.**
+"[Environment notes](#environment-notes)" below.** If you need Notcurses on
+Ubuntu Focal (20.04 LTS), you can run:
+
+```sh
+sudo add-apt-repository ppa:dankamongmen/notcurses
+sudo apt-get update
+```
 
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