What are the odds of being able to get my 20 year old RiscOS3, ARM3 software going on a current RiscOS RasPi ?
I, too, have been away from RISCOS scene for a long time now. I suspect your odds are very low. Programs then were compiled for 26bit arcitecture of the ARM chips at the time. Modern ARM chips are either 32bit or 64bit. The newer RISCOS' have been compiled for the 32bit arcitecture. I believe there is a program that will emulate a 26 bit environment. It is not, however, free software. I think it is called ARMULATE; or something like that. The best place to go for advice is the RiscOS forums at:
Hope this has been of some use.