You should call the following CMake commands to use the Qt6::Protobuf module in your project:

find_package(Qt6 REQUIRED COMPONENTS Protobuf)

target_link_libraries(mytarget PRIVATE Qt6::Protobuf)

You can use the qt_add_protobuf CMake command to implicitly call Qt Protobuf code generation for your project.

Using qt_add_protobuf

cmake_minimum_required(VERSION 3.16...3.22)
project(MyThings)

find_package(Qt6 REQUIRED COMPONENTS Protobuf)
qt_standard_project_setup()

qt_add_protobuf(MyMessages
    GENERATE_PACKAGE_SUBFOLDERS
    PROTO_FILES
        path/to/message.proto
        path/to/other_message.proto
    PROTO_INCLUDES
        /path/to/proto/include
)

qt_add_executable(MyApp main.cpp)

target_link_libraries(MyApp PRIVATE MyMessages)

In the example above, we generate a library called MyMessages, which contains the message types defined in the paths passed to the PROTO_FILES option. The GENERATE_PACKAGE_SUBFOLDERS option to generate a folder structure for the generated files. And the PROTO_INCLUDES option tells protoc to look for dependencies or imports in the specified directories. We create a target for an executable called MyApp, which we link to the MyMessages library.