There are several scripts available that can help you to install Magento with Nginx, MySQL, and Varnish on Ubuntu 20. Here are a few options:
Magento2 Auto Installer: This script provides a one-click installer for Magento 2 on Ubuntu 20 with Nginx, MySQL, and Varnish. You can find the script and instructions on GitHub: https://github.com/magenx/Magento-2-Auto-Installer-Ubuntu-20.04
Magento 2 Nginx Installer: This is another script that can help you to install Magento 2 on Ubuntu 20 with Nginx, MySQL, and Varnish. You can find the script and instructions on GitHub: https://github.com/MagePsycho/magento2-nginx-ssl-varnish
MageStack: MageStack is a complete hosting solution for Magento that includes Nginx, MySQL, and Varnish. It can be installed on Ubuntu 20 with a one-click installer. You can find more information and instructions on the MageStack website: https://magestack.com/
It's important to note that before using any of these scripts, you should ensure that your server meets the minimum system requirements for Magento 2 and that you have backups of your data in case of any issues during the installation process.