tengine | A distribution of Nginx with some advanced features | Runtime Evironment library

I think the issue is that you are serializing a List => for the serializer these are only MFModifier no MFTModifier

From Script Seialization:

No support for polymorphism

If you have a public Animal[] animals and you put in an instance of a Dog, a Cat and a Giraffe, after serialization, you have three instances of Animal.

One way to deal with this limitation is to realize that it only applies to custom classes, which get serialized inline. References to other UnityEngine.Objects get serialized as actual references, and for those, polymorphism does actually work. You would make a ScriptableObject derived class or another MonoBehaviour derived class, and reference that. The downside of this is that you need to store that Monobehaviour or ScriptableObject somewhere, and that you cannot serialize it inline efficiently.

The reason for these limitations is that one of the core foundations of the serialization system is that the layout of the datastream for an object is known ahead of time; it depends on the types of the fields of the class, rather than what happens to be stored inside the fields.

I managed o make it work with some extras in curl curl -XGET -H "Content-type: application/json" 'https://www.binance.com/gateway-api/v1/friendly/lending/project/customizedFixedProject/list?pageSize=3&pageIndex=1&status=ALL'

I know that ANSI code cannot display UTF-8 code, how could I convert ANSI to UTF-8?

There is no such encoding as "ANSI". If you mean ASCII (aka ANSI_X3.4-1968), then there is no need to do anything because ASCII is also valid UTF-8 as is.

If the content is already in UTF-8 (as the charset header implies), then converting to UTF-8 from another encoding makes no sense.

I use Linux

If you meant that you want to convert from UTF-8 to ASCII, then I would like to point out that it is quite likely that your terminal (emulator) is configured to use UTF-8 in which case such conversion would be counter-productive. Also, note that if the content has characters that don't exist in the target encoding, then they cannot be shown.

If it is actually true that you need to convert between UTF-8, and some other encoding (and that conversion if not from ASCII to UTF-8), then you'll find that C++ has no standard way to perform such conversion. You can either read the specifications for the respective encodings and implement the conversion yourself which is non-trivial and probably not something that would fit in a stack overflow answer, or (as is nearly always the better option) you can save time by using an implementation written by someone else.

What you really probably need to do first is pay attention to this header:

Content-Encoding: gzip

And conclude that the response is not text, but instead binary result of a compression algorithm, and you need to decompress it to make it readable. There are no standard (de-)compression functions in C++ either.