pi@raspberrypi:~ $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description:    Raspbian GNU/Linux 10.3 (buster)
Release:        10.3
Codename:       buster

Wander over to https://dotnet.microsoft.com/download/dotnet-core/scripts and you’ll find the installation script. You can download the bash script and execute it.

pi@raspberrypi:~ $ bash dotnet-install.sh
dotnet_install: Warning: Unable to locate zlib. Probable prerequisite missing; install zlib.
dotnet-install: Downloading link: https://dotnetcli.azureedge.net/dotnet/Sdk/3.1.201/dotnet-sdk-3.1.201-linux-arm.tar.gz
dotnet-install: Extracting zip from https://dotnetcli.azureedge.net/dotnet/Sdk/3.1.201/dotnet-sdk-3.1.201-linux-arm.tar.gz
dotnet-install: Adding to current process PATH: `/home/pi/.dotnet`. Note: This change will be visible only when sourcing script.
dotnet-install: Installation finished successfully.

Then it’s just a simple case of adding /home/pi/.dotnet to your system PATH variable.

pi@raspberrypi:~ $ dotnet --version
3.1.201

Wondering about the missing pre-requisite for zlib – so was I. The installer is looking for zlib via a ldconfig command. It seems package zlib1g-dev installs it as libz so the check fails. I’ll update this post if I run into any actual problems.