Just another option to choose from.
If you are looking for stable, production ready lib you are better off using something like LanguageExt.Core.
Most C# optional implementations use structs for better performance, which makes a lot of sense.
This lib instead uses separate classes to model optional objects. The benefit here is that "if" C# gets discriminated unions, then this model will fit in nicely and allow for idiomatic code.
So in short, at this point, its a gamble + fun side project to learn more about functional style in C# where performance is not a primary concern.