Which native cross platform framework to work with

i have a lot of experience with Java and C++ as such java is not option

When i say native i mean C++ cross platform . no electron here thanks ..

The app need to be :

1. Memory consumption should be as efficient as it can

2. Fast

3. access to OS api's

4. Mac , Linux , WIN

5. No OpenGL or such , it is heavy data driving app. with interfacing to external HTTPS / WebSockets / FTP / TCP

6. Currently it planned to be open source but it can be closed in some time in the future

Please from your experience Pros/Cons

Thanks!