The specific packages (6.18/6.19) you linked to are for Ubuntu 20.04, which is two years old, not "latest" by a long, long road. Latest supported would be version 1:6.0+dfsg-2expubuntu1.1, used by Ubuntu 21.10. Latest testing would be version 1:6.0+dfsg-2expubuntu4.

• 6.19 is in the focal-updates pocket of the Ubuntu repositories. Check that you really do have focal-updates enabled. Look at the changelog date -- it less than a week, you might be delayed by phased updates (if so, just be patient).

In order to run a specific version of the qemu package, you must satisfy all the dependencies. The simplest way to do that is to run the appropriate release of Ubuntu. That's how Debian-based systems work -- you avoid dependency hell using snapshots when the entire archive is built to a common set of dependencies.

If you try to bolt newer software onto an older release of Ubuntu, it might work. It might not. It might cause unexpected problems. The Debian way to avoid such problems is to upgrade from one snapshot to the next. Each snapshot is a release. Ubuntu releases every 6 months in April and October.

So there's no point "requesting" a package. It's not about permission. It's about dependencies.

If there is really some feature in newer versions of qemu that you want, use a newer release of Ubuntu...or a snap of qemu on an older release. If you merely just want a great recent version of qemu, then use the version apt installs in your 20.04 system.

I had the same problem and this fixed it for me

sudo apt-get install qemu-user-static=1:4.2-3ubuntu6.17

I actually put this in the run section:

$ apt-cache madison qemu-user-static
$ sudo apt-get install qemu-user-static=1:4.2-3ubuntu6.17

so I know what versions are available