Here are the instructions I followed to install .NET on Ubuntu 20.04.1 LTS.

1. Add Microsoft signing key and repository to apt (see details in /etc/apt).

   wget https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
   sudo dpkg -i packages-microsoft-prod.deb

2. Install .NET SDK (no runtime needed).

   sudo apt-get update; \
   sudo apt-get install -y apt-transport-https && \
   sudo apt-get update && \
   sudo apt-get install -y dotnet-sdk-5.0

Made by following this tutorial.

To generate the code, use:

dotnet new console -o helloWorld

To run the project, cd into the helloWorld folder and enter:

dotnet run