Googled the problem and found the flange shaft assembly was a likely culprit. I dismantled the washer which was not too difficult. Key steps were
Follow the AppliancePartsPro video for shock absorber replacement up until unbolting the shocks.
Remove the support bar for the water inlet hosing on the top of the machine (screws are the front, slots in the back) and fold these and the dispenser tray holder back out of the way.
Remove the top bracket the holds the control panel.
Remove the large red counter weights from the drum
Unbolt the front shocks from the plastic drum
Unbolt the front half of the plastic drum - the only difficult bit is disengaging the support spring that faces front to back - you have to lift the drum and flex the spring sideways.
You need to remove the heater wiring, and a couple of pipes from the front half of the drum then lift the front half off.
Lastly remove the drive rotor at the rear by undoing the single large bolt and the inner rotating steel drum should slide out.
My flange was in three pieces so had collapsed completely.
For the replacement I coated it with four coats of Plasti-Dip a rubberised coating compound and hope this prevents and early repeat.
Reassembly was not difficult - one tip is to make sure the heater coil does not get bent during handling the front drum half - it can scrape against the reinstalled inner rotating drum.
I replaced nothing else. The main bearing seems fine
In defence of Samsung machines, ours had a very heavy load for a large family running several times daily for four and half years before this failure. With this $120 part replace it is back to perfect operation. In all other respects it has been the best washer we have ever owned.