Strange fallback RIDs

Describe the bug

I recently install dotnet on manjaro, a arch like distro, and noticed I have issues running unless I specify runtime. While digging a little with the people on the runtime repo we noticed strange behavior related to the fallback RID. It was suggested I wrote a ticket here as well, as it looked like it was related to the SDK(?)

Below is COREHOST_TRACEFILES default.txt arch-x64.txt linux-x64.txt

If you search for “fallback graph” you will see that the graph is really small for default and arch-x64, while linux-x64 seems to contain all distros(?)

It is my understanding that the fallback graph for arch-x64 should also contain a linux-x64 => [ ... ] which is missing. Any idea what might have caused it?

To Reproduce

Run COREHOST_TRACE=1 COREHOST_TRACEFILE=linux-x64.txt dotnet run -r linux-x64 and COREHOST_TRACE=1 COREHOST_TRACEFILE=arch-x64.txt dotnet run -r arch-x64 and compare the results in the corefile.

Further technical details

[tobias@tobias-expertbook ~]$ dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100
 Commit:    9e8b04bbff

Runtime Environment:
 OS Name:     manjaro
 OS Version:  
 OS Platform: Linux
 RID:         arch-x64
 Base Path:   /usr/share/dotnet/sdk/6.0.100/

Host (useful for support):
  Version: 6.0.0
  Commit:  4822e3c3aa

.NET SDKs installed:
  6.0.100 [/usr/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

[vitek-karas]

It’s possible this is “from” NuGet (SDK uses NuGet assemblies to deal with some of the complexities around RID graph), but it’s as well possible it’s not there - we need somebody to investigate.

[vitek-karas]

For context - the original discussion which found this is here: https://github.com/dotnet/runtime/pull/63338.