I have an ARM64 laptop where I installed WSL2 running Ubuntu 18.04. I made sure to install vsdbg in Ubuntu, as well as dotnet, from a PPA. So all the requirements are met - I can also build the dotnet/runtime repo without problems.
But when I try to install the OmniSharp extension inside WSL2, I get this error dialog:

Notice the architecture name. It was detected as "aarch64". I suspect the architecture may be considered "unknown", even though the WSL2 architecture is actually "aarch64" when running inside an ARM64 machine. Here's the output of "uname":
carlos@armlaptop:~$ uname -a
Linux armlaptop 4.19.121-microsoft-standard #1 SMP Fri Jun 19 21:03:36 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux
This error is also preventing me from debugging. I have a configuration in launch.json, which works in another laptop (it's x64), but in my ARM64 laptop I get this error:

Let me know if you need more information.
cc @pgovind
ARM64 is not supported yet see https://github.com/OmniSharp/omnisharp-roslyn/pull/1706
Thanks for letting us know, @filipw.
I'll close this issue in favor of #1706. cc @JoeRobich.
Reopening because PR https://github.com/OmniSharp/omnisharp-roslyn/pull/1706 was only exploratory and won't address this.
I was exploring the viability of doing .Net in a Raspberry Pi 4 (8bg model) and while you can deploy .Net without any issues, developing/debugging is out of reach at the momtent

I received the same error when trying to write C# using my Pi400. Since VS Code AND .net 5 runs perfectly and out of the box on the RaspberryPi now, it's time to port OmniSharp to a linux ARM64 architecture, so we can use the Raspberry Pi 400 (and others) for teaching purposes and fooling around in .NET 5 (and above).
Agreed. @filipw what needs to be done to increase the priority of this issue?
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I received the same error when trying to write C# using my Pi400. Since VS Code AND .net 5 runs perfectly and out of the box on the RaspberryPi now, it's time to port OmniSharp to a linux ARM64 architecture, so we can use the Raspberry Pi 400 (and others) for teaching purposes and fooling around in .NET 5 (and above).