1. Create netstandard2.0 class library: dotnet new classlib --framework "netstandard2.0" -o KiotaTest
2. Set LangVersion to 7.3 in the csproj file.
3. Add Kiota dependencies:

dotnet add package Microsoft.Kiota.Abstractions
dotnet add package Microsoft.Kiota.Http.HttpClientLibrary
dotnet add package Microsoft.Kiota.Serialization.Form
dotnet add package Microsoft.Kiota.Serialization.Json
dotnet add package Microsoft.Kiota.Serialization.Text
dotnet add package Microsoft.Kiota.Serialization.Multipart

4. Add file events-api.yml.
5. Generate API client. kiota generate -l CSharp -c EventsClient -n KiotaEvents.Client -d ./events-api.yml -o ./Client --clean-output
6. Build.

Build Output:
[...]KiotaTest\Client\Events\EventsRequestBuilder.cs(20,88): error CS0246: The type or namespace name 'DateOnly' could not be found (are you missing a using directive or an assembly reference?) [...]