You’re missing the Kicksecure repository. Since Whonix 17, both, Whonix and Kicksecure repositories need to be enabled in Whonix. To enable:
sudo repository-dist --enable --repository stable
Then please re-check that file.
(Whonix is based on Kicksecure.)
It’s a upgrade migration bug that you’re missing that repository and that the release-upgrade script did not advice on that beforehand.
This issue is unspecific to KVM / VIrtualBox / Qubes. These are all using the same repositories. [1]
[1] (Except Qubes-Whonix having the Qubes repository enabled by default but that’s not important and besides the pont.)