OCSP support did not arrive in .NET Core until 3.0 (https://github.com/dotnet/corefx/pull/35367) and we currently do not test against it. When we add support for netstandard 2.1 or decide to explicitly test against .NET Core 3.0 we should re-enable the OCSP tests.
Currently all TLS related tests are disabled on Linux and would also need to be re-enabled.