Deep cloning objects has been a major pain point for me for a long time. Recently, I've run into a case where after cloning a dictionary ContainsKey no longer worked for items cloned.
This inspired me to create a new library FastCloner for the modern .NET Core that would just work. Out of the box. Cyclic references, delegates, read-only collections... as many edge cases covered as possible.
There are still some scenarios, unmanaged memory for example, where cloning can go awry, but it should be a major improvement of the prior art. Feel free to check it out!