When attempting to install Virtualbox on Debian Testing, I'm getting a 404 error from the repository after I've added it.
Contents of apt update:
Hit:1 http://ftp.us.debian.org/debian testing InRelease
Ign:2 http://download.virtualbox.org/virtualbox/debian testing InRelease
Err:3 http://download.virtualbox.org/virtualbox/debian testing Release
404 Not Found [IP: 23.218.90.109 80]
Reading package lists... Done
E: The repository 'http://download.virtualbox.org/virtualbox/debian testing 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.
Contents of /etc/apt/sources/list:
#
# deb cdrom:[Debian GNU/Linux testing _Buster_ - Official Snapshot amd64 xfce-CD Binary-1 20190107-04:42]/ buster main
# deb cdrom:[Debian GNU/Linux testing _Buster_ - Official Snapshot amd64 xfce-CD Binary-1 20190107-04:42]/ buster main
deb http://ftp.us.debian.org/debian/ testing main
deb-src http://ftp.us.debian.org/debian/ testing main
# This system was installed using small removable media
# (e.g. netinst, live or single CD). The matching "deb cdrom"
# entries were disabled at the end of the installation process.
# For information about how to configure apt package sources,
deb http://download.virtualbox.org/virtualbox/debian testing contrib
# deb-src http://download.virtualbox.org/virtualbox/debian testing contrib
# see the sources.list(5) manual.
Due to using Debian Testing instead of Stable/Stretch, I had to install VirtualBox like it's installed for Ubuntu 18.0.4. Instructions for this I found here: https://www.itzgeek.com/how-tos/linux/ubuntu-how-tos/install-virtualbox-4-5-ubuntu-16-04.html