I meant install the PinballX .net framework version (not the actual .net 4 runtime).
The PinballX installer includes .net core and .net framework versions, the default install is .net core but if you change the compatibility mode of the PinballX installer it can install the framework version of PinballX instead (which has the same version number and updates as the core version). The PinballX log file will indicate on the first line which flavour is installed.