I just upgraded to net8.0 from 6.0 in a repo, and ran dotnet restore, which worked fine.

Upon running the build and restoring dependencies after opening a PR, Github gives the error:

/home/runner/.dotnet/sdk/7.0.408/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.TargetFrameworkInference.targets(160,5): 
error NETSDK1045: The current .NET SDK does not support targeting .NET 8.0.  
Either target .NET 7.0 or lower, or use a version of the .NET SDK that supports .NET 8.0. Download the .NET SDK from https://aka.ms/dotnet/download [/home/.../Client.csproj]

running dotnet --version locally gives me 8.0.24, so the SDK is at 8.0.