Update your software lists; your issue shows a user-level or procedural error. I picked a package at random in your paste & the package available is
qemu-system-common | 1:4.2-3ubuntu6 | focal | amd64, arm64, armhf, ppc64el, riscv64, s390x
qemu-system-common | 1:4.2-3ubuntu6.24 | focal-security | amd64, arm64, armhf, ppc64el, riscv64, s390x
qemu-system-common | 1:4.2-3ubuntu6.24 | focal-updates | amd64, arm64, armhf, ppc64el, riscv64, s390x
qemu-system-common | 1:4.2-3ubuntu6.25 | focal-proposed | amd64, arm64, armhf, ppc64el, riscv64, s390x
but your system with it's outdated lists is looking for 1:4.2-3ubuntu6.21
Your issue is the lack of security fixes & updates & system being very outdated.
A full-upgraded Ubuntu 20.04 LTS system will report as Ubuntu 20.04.6 but yours is reporting as 20.04.2 ? as you've not applied security fixes or updates since before August 2021.
Please note the ISO release date links I provided are for new installs, installed systems received these updates a week+ before the ISO release date.
Use
sudo apt update
to update your software lists
sudo apt full-upgrade
to apply fixes
I hope your system is kept offline.