Upstream Linux has moved to libgpiod. This is maintained by Bartosz and the userspace tools are also maintained by him. For the mappings, you can either use libretech-wiring-tool to lookup the chip and line numbers or the precompiled GPIO maps.
For C or C++ bindings, you can find them here: libgpiod/bindings/cxx at master · brgl/libgpiod · GitHub
You can find the packaged library (libgpiod or libgpiod2) included in most Linux distributions.