Ironically, while LLVM lives on, Clang is slowly dying and is failing to compete with GCC. Clang's C++20 support lags behind GCC because both of its major corporate sponsors, Google and Apple, have seemingly moved on (after failing to get the ABI changed, Google went over to working on Carbon, and Apple doesn't care as long as the C++ support is good enough to compile LLVM and the C++14 subset required for Metal's shading language). All the other vendors who take advantage of Clang's permissive licensing seem unwilling to upstream improved C++ support.