*Important -- select Linux Mint as mirror server "Americal Flag" 🇺🇸 for packages, if not it will show error packages.linuxmint.com is unreachable, after upgrade you can change to your local mirror server as before. or you can edit the /etc/apt/source.list.d/official-package-repositories.list, replace the virginia main line with "deb fastly.linuxmint.io virginia main upstream import backport" save the file. Then $ sudo apt update