Update error “apt-get update”

Question

When I update to "sudo apt-get update" appears this errors into terminal. How can I solved it? Thanks!

(...)
Err:6 https://dl.bintray.com/aluxian/deb <channel>/main amd64 Packages
  404  Not Found
(...)
W: The repository 'https://dl.bintray.com/aluxian/deb <channel> Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: No s'ha pogut obtenir https://dl.bintray.com/aluxian/deb/dists/<channel>/main/binary-amd64/Packages  404  Not Found
E: Alguns índex no s'han pogut baixar. S'han descartat, o en el seu lloc s'han emprat els antics.

Answer 1

after googling your repository i deduced that you want to install facebook messenger desktop :)

so follow these instructions as said on github

sudo apt-key adv --keyserver pool.sks-keyservers.net --recv 6DDA23616E3FE905FFDA152AE61DA9241537994D

2nd step, he said replace with stable, beta or dev so result can be (the recommended one is stable but you can also try the dev or beta one and you can uninstall it if it has a problem :

echo "deb https://dl.bintray.com/aluxian/deb/ stable main" |
  sudo tee -a /etc/apt/sources.list.d/aluxian.list

or

echo "deb https://dl.bintray.com/aluxian/deb/ beta main" |
  sudo tee -a /etc/apt/sources.list.d/aluxian.list

or

echo "deb https://dl.bintray.com/aluxian/deb/ dev main" |
  sudo tee -a /etc/apt/sources.list.d/aluxian.list

after that:

sudo apt update
sudo apt install messengerfordesktop

Answer 2

Try removing all the repository source with 404 error code, In case you would like to automate the same,

Go Here

Once the ppa's that are not found are removed apt-get update will work just fine.