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"Hash Sum mismatch" printed by `apt-get` on Debian and derivatives means that the file as downloaded had a different cryptographic checksum (hash) than what's listed in the packages list.

In this case, the package list is the one at http://us.archive.ubuntu.com/ubuntu/dists/focal-updates/main/binary-amd64 which lists the expected SHA256 hash as 9d469246b988425afdfef1011f72cfc6ece473e4dd35193005a81c7b73d865b6, consistent with what you show but not with the file that apparently ends up being downloaded.

There are four main reasons that I can think of why you might see such an error:

 * The package archive is in the process of being updated; this seems unlikely, and if that's the case, the situation should be resolved soon and after at most an `apt-get update`
 * There is an error in the packaging process (basically, the distribution vendor screwed up somewhere); if so, if the situation isn't resolved soon, you should file a bug report with them against the affected package
 * Your system is somehow misconfigured, and you need to figure out why it's downloading mismatched package manifests and package files; however, if that were the case, I would expect you to be having similar difficulties with most or all packages, not just a single one
 * There is an active attack going on somewhere, causing you to receive different packages lists and actual package files; in this case, the tools are doing their job by preventing you from installing packages with unexpected, unknown and potentially dangerous contents

You can try to spin up a VM with the same release of Ubuntu and no customizations and try to install the affected package there; if *that* works, it's likely something local to your system, and you need to figure out in what way it's misconfigured and how to fix that (which is decidedly not a software development problem, but might very well be a [Linux](https://linux.codidact.com/) question).

If that doesn't work either, and the situation doesn't get resolved in a day or two at most and with no more action on your part than an `apt-get update`, especially if you haven't made changes to your package manager configuration around the time when this started, then you are likely justified in filing a bug report against the affected package and distribution version with your distribution vendor.