Out of my personal go-to c++ libs, the only ones I missed are the stb libraries (https://github.com/nothings/stb/, in particular the image ones are very popular) and maybe ImGui, but that might be too niche.

Also I would love to have a nice c++ lib for uuids. It's in boost of course.. but well that's boost. Outside of that there is one, but it requires GSL.

stb is C89 though and this site seems to be focusing on C++ stuff.

The site focuses on C++11 and newer. AFAIK Dear ImGui is almost C code, using just a few C++98 features.

Right, missed the modern part