pi@raspberrypi:~ $ sudo apt-get update
Hit:1 http://archive.raspberrypi.org/debian stretch InRelease
Hit:2 http://raspbian.raspberrypi.org/raspbian stretch InRelease
Ign:3 https://dl.bintray.com/etcher/debian stable InRelease
Get:4 https://dl.bintray.com/etcher/debian stable Release [3,674 B]
Get:5 https://dl.bintray.com/etcher/debian stable Release.gpg [821 B]
Ign:5 https://dl.bintray.com/etcher/debian stable Release.gpg
Fetched 4,495 B in 1s (2,470 B/s)
Reading package lists... Done
W: GPG error: https://dl.bintray.com/etcher/debian stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 379CE192D401AB61
W: The repository 'https://deb.etcher.io stable Release' is not signed.
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.
N: Skipping acquire of configured file 'etcher/binary-armhf/Packages' as repository 'https://deb.etcher.io stable InRelease' doesn't support architecture 'armhf'
Is there a way to remove that problematic url from the list that is checked whenever "apt-get update" is run?
All the repository URL's are in the apt source files.
The main source file is /etc/apt/sources.list. You can edit the file with e.g. nano to remove the offending 'etcher' line(s):
sudo nano /etc/apt/sources.list
You also need to check the 'secondary' list files. That is any .list file in directory /etc/apt/sources.list.d/. You should find e.g. raspi.list in there, which points to the RPF repositories. You need to check all the list files in there and if necessary edit the file.
/etc/apt/sources.list? If not, do you know how these other sources were added?