Got it working perfectly under W98SE un PCEM
https://pcem-emulator.co.uk/I think that 1.5 version with radar fix and gouard shading is only for Windows. DOS version was never updated to 1.5.
You can patch 1.0 version up to 1.2a. 1.5 is part of paid datadisc or Squadron Edition that contains datadisc as well as 1.5 changes.