Remove .NET 8 and .NET 9 targets after November 10, 2026 #295

Summary

After .NET 8 reaches end of support on November 10, 2026, remove the net8.0 and net9.0 targets from the libraries and tests that still multi-target them. .NET 9 reached end of support on May 12, 2026, so both targets can be retired together at that point.

Do not merge this change before November 10, 2026.

Acceptance criteria

• Remove net8.0 and net9.0 from all affected TargetFrameworks declarations.
• Retain netstandard2.0 where it is currently part of the compatibility contract.
• Retain net10.0 as the supported modern .NET target.
• Remove or simplify target-specific MSBuild conditions and package references that are no longer needed.
• Update CI, documentation, and package compatibility statements that refer to .NET 8 or .NET 9 support.
• Verify the full solution builds and the supported test matrix passes.
• Confirm produced NuGet packages no longer contain net8.0 or net9.0 assets.

Reference: https://dotnet.microsoft.com/platform/support/policy/dotnet-core