Adjust for new NLSR configuration format

Also removes 20.04 LTS from officially supported distros
as it no longer runs "out of the box" due to recent commits.

Refs #5366, #5367

Change-Id: I30577bd9010e7597e00a8826d5e31d5487ef14e2
diff --git a/docs/install.rst b/docs/install.rst
index 9a04804..5dc7597 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -6,14 +6,16 @@
 
 Mini-NDN is officially supported on the following Linux distributions:
 
-- Ubuntu 20.04
 - Ubuntu 22.04 (recommended)
-- Ubuntu 24.04
 - Debian 11 (WiFi scenario does not work)
 - Fedora 33 (WiFi scenario does not work)
 
 You must have sudo privileges to install and run Mini-NDN.
 
+Ubuntu 20.04 LTS is no longer supported as of v0.8.0, but users may still use the v0.7.0 release.
+
+Ubuntu 24.04 LTS is not currently supported due to issues with required libraries no longer being updated.
+
 Using Docker
 ------------