[SOLVED] Apt and sources modernization

[Princey]

I've been putting off the request to modernization request for customized (personally added) repositories for some time. With a few extra minutes to spare, I read up on whether the act of non-modernized sources will affect the system moving forward or not. Frankly, it doesn't affect the system but to get rid of that annoyance every time I run updates via the terminal, I finally did it sometime last week. This week, while running updates, I'm presented with a new issue. Some of the entries such as Google Chrome and virtualbox now throw out some warning messages of not supporting i386. I'm certain Virtualbox did specify in the source file

deb [arch=amd64]

However, it is exempted or removed with the modernized version and I've tried entering it on the first and second line (each try done separately) with NO success. Before modernization, it was on the uri line

deb [arch=amd64 signed-by=/usr/share/keyrings/oracle-virtualbox-2016.gpg] https://download.virtualbox.org/virtualbox/debian oracular contrib​

(There's no repository for Plucky. Uses the same deb package for Oracular). Apt throws a warning that there's malformed entry and won't update unless I remove the addition.

Question is, how, with the new modernization of the sources list can the entry be fixed? Here's the modernized version of Virtualbox (Chrome is almost identical of course)

Types: deb
URIs: https://download.virtualbox.org/virtualbox/debian/
Suites: oracular
Components: contrib
Signed-By:/usr/share/keyrings/oracle-virtualbox-2016.gpg

[Princey]

Okay, having slept on this, I decided to do a comprehensive search and read-up on apt, sources.list with the new changes brought on over the past year or so. Solution was simpler than I imagined, just had to do some more reading. I'm posting here in case someone has the same issue. The fix is an extra line that needs to be added, in particular, "architectures". Note, it's plural not singular. Example of a sources list using the same virtualbox I had listed earier:

Types: deb
URIs: [URL]https://download.virtualbox.org/virtualbox/debian/[/URL]
Suites: oracular
Components: contrib
Signed-By:/usr/share/keyrings/oracle-virtualbox-2016.gpg​
Architectures: amd64

This works for all sources.list that give the i386 error.