See microsoft.com article
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# Prerequisites
# Update the list of packages
sudo apt-get update
# Install pre-requisite packages.
sudo apt-get install -y wget apt-transport-https software-properties-common
# Get the version of Ubuntu
source /etc/os-release
# Download the Microsoft repository keys
wget -q https://packages.microsoft.com/config/ubuntu/$VERSION_ID/packages-microsoft-prod.deb
# Register the Microsoft repository keys
sudo dpkg -i packages-microsoft-prod.deb
# Delete the Microsoft repository keys file
rm packages-microsoft-prod.deb
# Update the list of packages after we added packages.microsoft.com
sudo apt-get update
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# Install PowerShell
sudo apt-get install -y powershell
# Start PowerShell
pwsh