Encountered this today where there were no issues before, console logs follow:
Hit:3 https://download.virtualbox.org/virtualbox/debian bionic InRelease
N: Skipping acquire of configured file 'contrib/binary-i386/Packages' as repository 'https://download.virtualbox.org/virtualbox/debian bionic InRelease' doesn't support architecture 'i386'
Is this a problem with the repository, or with my own config? The same operation had no issue as recently as 3 days ago.
Manual comparison of previous 16.04 LTS folder structure
with current 18.04 LTS folder structure
gives interesting result: it seems that Oracle dropped 32 bit for bionic repository.
See information on official Downloads page:
VirtualBox binaries
By downloading, you agree to the terms and conditions of the respective license.
If you're looking for the latest VirtualBox 5.2 packages, see VirtualBox 5.2 builds. >Please also use version 5.2 if you still need support for 32-bit hosts, as this has been discontinued in 6.0. Version 5.2 will remain supported until July 2020.
So you should change repository line in the /etc/apt/sources.list.d/virtualbox.list to
deb [arch=amd64] http://download.virtualbox.org/virtualbox/debian bionic contrib
