Consolidate Linux installation docs

- Move all Linux installation docs to the separate page to eliminate repetition
- Indicate that only Ubuntu 20.04 is supported for apt-add-repository method
- Pull openSUSE/SUSE out of the "unofficial" section since it refers to
  downloading our official packages
- Point out manual installation methods as well

README.md

@@ -68,6 +68,10 @@ Upgrade:
 sudo port selfupdate && sudo port upgrade gh
 ```
 
+### Linux
+
+See [Linux installation docs](/docs/install_linux.md).
+
 ### Windows
 
 `gh` is available via [scoop][], [Chocolatey][], and as downloadable MSI.
@@ -105,42 +109,6 @@ choco upgrade gh
 
 MSI installers are available for download on the [releases page][].
 
-### Debian/Ubuntu Linux
-
-Install:
-
-```bash
-sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-key C99B11DEB97541F0
-sudo apt-add-repository -u https://cli.github.com/packages
-sudo apt install gh
-```
-
-Upgrade:
-
-```
-sudo apt update
-sudo apt install gh
-```
-
-### Fedora, Centos, Red Hat Linux
-
-Install:
-
-```bash
-sudo dnf config-manager --add-repo https://cli.github.com/packages/rpm/gh-cli.repo
-sudo dnf install gh
-```
-
-Upgrade:
-
-```bash
-sudo dnf install gh
-```
-
-### Other Linux
-
-See [Linux installation docs](/docs/install_linux.md)
-
 ### Other platforms
 
 Download packaged binaries from the [releases page][].
@@ -149,6 +117,7 @@ Download packaged binaries from the [releases page][].
 
 See here on how to [build GitHub CLI from source][build from source].
 
+
 [official docs]: https://cli.github.com/manual
 [scoop]: https://scoop.sh
 [Chocolatey]: https://chocolatey.org

docs/install_linux.md

@@ -1,15 +1,15 @@
 # Installing gh on Linux
 
-The core, paid developers of `gh` officially support a `.deb` repository and a `.rpm` repository. We
-primarily test against Ubuntu and Fedora but do our best to support other distros that can work with
-our repositories. We focus on support for `amd64` and `i386` architectures.
+Packages downloaded from https://cli.github.com or from https://github.com/cli/cli/releases
+are considered official binaries. We focus on a couple of popular Linux distros and
+the following CPU architectures: `386`, `amd64`, `arm64`.
 
-All other combinations of distro, packaging, or architecture should be considered community
-supported.
+Other sources for installation are community-maintained and thus might lag behind
+our release schedule.
 
-## Official methods
+## Official sources
 
-### Debian/Ubuntu Linux (apt)
+### Debian, Ubuntu 20.04 Linux (apt)
 
 Install:
 
@@ -21,7 +21,7 @@ sudo apt install gh
 
 Upgrade:
 
-```
+```bash
 sudo apt update
 sudo apt install gh
 ```
@@ -41,18 +41,27 @@ Upgrade:
 sudo dnf install gh
 ```
 
-## Community supported methods
+### openSUSE/SUSE Linux (zypper)
 
-### openSUSE/SUSE Linux
+It's possible that https://cli.github.com/packages/rpm/gh-cli.repo will work with zypper, but
+this hasn't been tested.
 
-It's possible that https://cli.github.com/packages/rpm/gh-cli.repo will work with zypper but it
-hasn't been tested. Otherwise, to install from package:
+## Manual installation
+
+* [Download release binaries][releases page] that match your platform; or
+* [Build from source](./source.md).
+
+### openSUSE/SUSE Linux (zypper)
  
 Install and upgrade:
 
 1. Download the `.rpm` file from the [releases page][];
 2. Install the downloaded file: `sudo zypper in gh_*_linux_amd64.rpm`
 
+## Community-supported methods
+
+Our team does do not directly maintain the following packages or repositories.
+
 ### Arch Linux
 
 Arch Linux users can install from the [community repo][arch linux repo]:
@@ -69,4 +78,6 @@ Android users can install via Termux:
 pkg install gh
 ```
 
+
+[releases page]: https://github.com/cli/cli/releases/latest
 [arch linux repo]: https://www.archlinux.org/packages/community/x86_64/github-cli