Add note to the README about not using Snap or Flatpak versions

Fixes https://github.com/fwupd/fwupd/issues/2543

README.md

@@ -3,8 +3,6 @@ fwupd
 [![Build Status](https://travis-ci.org/fwupd/fwupd.png?branch=master)](https://travis-ci.org/fwupd/fwupd)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/10744/badge.svg)](https://scan.coverity.com/projects/10744)
 
-[![Get it from the Snap Store](https://snapcraft.io/static/images/badges/en/snap-store-white.svg)](https://snapcraft.io/fwupd)
-
 This project aims to make updating firmware on Linux automatic, safe and reliable.
 
 Additional information is available at the website: https://fwupd.org/
@@ -13,6 +11,21 @@ Additional information is available at the website: https://fwupd.org/
 
 The most up to date compilation instructions are available in the [Wiki](https://github.com/fwupd/fwupd/wiki/Compilation).
 
+**NOTE:** In most cases end users should never compile fwupd from scratch; it's a
+complicated project with dozens of dependencies (and as many configuration options)
+and there's just too many things that can go wrong.
+
+Users should just have fwupd installed and updated by their distro, managed and
+tested by the package maintainer.
+The distribution will have also done some testing with how fwupd interacts with
+other software on your system, for instance using GNOME Software.
+
+Installing fwupd using [Snap](https://github.com/fwupd/fwupd/wiki/fwupd-snap)
+or using [Flatpak](https://github.com/fwupd/fwupd/wiki/fwupd-flatpak) might be
+useful to update a specific device on the command line that needs a bleeding
+edge fwupd version, but it should not be considered as a replacement to the
+distro-provided system version.
+
 LVFS
 ----
 This project is configured by default to download firmware from the [Linux Vendor