[boost] Mixing C++ language versions

Can one mix compilation units or libraries built with different versions of C++? If I build my DLL with C++20, can a customer use it with their C++11 app? How are compiler and library vendors dealing with this? Do/will they supply multiple binaries for each C++ version? (I'm already building for each architecture plus release/debug. Adding the compiler version explodes the number of binaries to build and test.)