First you need to install the .NET 8.0 SDK, if you have some previous Ubuntu package installed, remove it:

$ sudo apt remove dotnet* aspnetcore* netstandard*

Now you can install the .NET from Microsoft, to you need to create this file:

$ sudo vi /etc/apt/preferences.d/99microsoft-dotnet.pref

With this content:

Package: *
Pin: origin "packages.microsoft.com"
Pin-Priority: 1001

Finally update and install it:

$ sudo apt update

$ sudo apt install -y dotnet-sdk-8.0

Finally clone the Meadow Core Samples:

 $ git clone https://github.com/WildernessLabs/Meadow.Core.Samples

Enter inside Cell_Basics:

$ cd Meadow.Core.Samples/Source/Cellular/Cell_Basics

Compile it:

$ dotnet build

Welcome to .NET 8.0!
---------------------
SDK Version: 8.0.102

----------------
Installed an ASP.NET Core HTTPS development certificate.
To trust the certificate, view the instructions: https://aka.ms/dotnet-https-linux

----------------
Write your first app: https://aka.ms/dotnet-hello-world
Find out what's new: https://aka.ms/dotnet-whats-new
Explore documentation: https://aka.ms/dotnet-docs
Report issues and find source on GitHub: https://github.com/dotnet/core
Use 'dotnet --help' to see available commands or visit: https://aka.ms/dotnet-cli
--------------------------------------------------------------------------------------
MSBuild version 17.8.5+b5265ef37 for .NET
Determining projects to restore...
Restored /comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/Cell_Basics.csproj (in 1.26 sec).
/comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/MeadowApp.cs(53,20): warning CS1998: This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread. [/comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/Cell_Basics.csproj]
Cell_Basics -> /comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/bin/Debug/netstandard2.1/App.dll

Build succeeded.

/comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/MeadowApp.cs(53,20): warning CS1998: This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread. [/comum/workspace/Consultancy/WildernessLabs/Meadow.Core.Samples/Source/Cellular/Cell_Basics/Cell_Basics.csproj]
1 Warning(s)
0 Error(s)

Time Elapsed 00:00:02.87