Referencing a Visual Studio project that targets the net5.0 framework, or a variant thereof like net5.0-windows7.0 etc, results in the output executable (.exe) not being enlisted underneath the Primary files category.
It does show up underneath the Companion files category, which can be used as a workaround. This workaround is however not a true solution because machine-local files like appsettings.development.json MUST NOT be copied into a released installer.
Because Net5.0 inherits the toolchain from .NetCore this is not wrong behaviour per se because the actual app code is contained within the main output library (.dll). The executable is nothing more than a bootstrapper for that library.
The executable is nonetheless required because both service entries and start menu tiles require an exe file to launch.