Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/focal-updates/main/dep11/Components-amd64.yml.xz File has unexpected size (274756 != 274728). Mirror sync in progress? [IP: 2801:82:80ff:8000::5 80]
Most likely, you happened to run the command while the Regional Server you are using was syncing.
There may be other causes- which are easy to fix, too.
But for now, let's focus on that most likely one.
Software & Updates
On the first open tab ; Software
Ensure that the Top Four Boxes are checked to ON.
Please set "Download from" to
Main Server in the drop down menu.
Reboot and test.