The repository does not have a Release File

Question

To install the Brave browser I followed the instructions from https://github.com/brave/browser-laptop/blob/master/docs/linuxInstall.md

curl https://s3-us-west-2.amazonaws.com/brave-apt/keys.asc | sudo apt-key add -
echo "deb [arch=amd64] https://s3-us-west-2.amazonaws.com/brave-apt `lsb_release -sc` main" | sudo tee -a /etc/apt/sources.list.d/brave-`lsb_release -sc`.list

but when I run sudo apt update i get the errors

Hit:1 http://br.archive.ubuntu.com/ubuntu xenial InRelease
Hit:2 http://br.archive.ubuntu.com/ubuntu xenial-updates InRelease                                                                                                       
Hit:3 http://br.archive.ubuntu.com/ubuntu xenial-backports InRelease                                                                                                     
Hit:4 http://packages.elementary.io/appcenter xenial InRelease                                                                                                  
Get:5 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]                                                                                      
Hit:6 http://ppa.launchpad.net/elementary-os/stable/ubuntu xenial InRelease       
Hit:7 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xenial InRelease                               
Ign:8 https://s3-us-west-2.amazonaws.com/brave-apt loki InRelease
Err:9 https://s3-us-west-2.amazonaws.com/brave-apt loki Release
  403  Forbidden
Reading package lists... Done
E: The repository 'https://s3-us-west-2.amazonaws.com/brave-apt loki Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Answer 1

I think the problem is the 'loki' part of 'https://s3-us-west-2.amazonaws.com/brave-apt loki Release'. Loki is the name of the latest Elementary OS release.

This happens because lsb_release -sc in the commands they instruct you to use returns the text "loki". You can try this by running:

echo `lsb_release -sc`

The install instructions are for Ubuntu and they assume it's replaced by a Ubuntu release like xenial. Since you are running ElementaryOS Loki, which is based on Ubuntu 16.04 (Xenial) (See: wiki) I would manually replace the lsb_release -sc parts with xenial. A bit like they advice for Linux Mint. So:

curl https://s3-us-west-2.amazonaws.com/brave-apt/keys.asc | sudo apt-key add -
echo "deb [arch=amd64] https://s3-us-west-2.amazonaws.com/brave-apt xenial main" | sudo tee -a /etc/apt/sources.list.d/brave-xenial.list
sudo apt update
sudo apt install brave-beta

(I hope these things will get easier in the near future by newer packaging solutions like Snaps and/or Flatpak.)