If you usually execute the apt update command from the terminal and you usually add custom apt sources you might face an error like the following:

E: The repository 'https://dl.bintray.com/resin-io/debian stable Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.

Basically the repository https://dl.bintray.com/resin-io/debian is no longer available.

How to fix the error

In order to fix it we might try to find the new repository, but in my case it was used to install an application that I’m no longer using, so I decided to remove it.

To do so, I opened the sources.list file with vim and root permissions:

sudo vim /etc/apt/sources.list

I searched for the line containing that broken repository:

deb https://dl.bintray.com/resin-io/debian stable etcher

And deleted it.

Then save and exit by pressing ESC and typing :wq.

If you try again with apt update, you shouldn’t get that error anymore.