I would recommend either upping to a discounted neo 1 or going elsewhere. I am currently waiting for tacx to come up with a warranty solution for my second broken flux. both broke the exact same way, started squealing and unable to hold target wattage steady. Second unit only lasted 16 rides before starting to squeal.
If you are constrained by budget here’s my understanding of the differences.
Flux S - new body to accommodate long cage derailleurs, slightly tweaked material internally to increase wattage floor control but not much different.
Flux 2 - New internals with a larger flywheel to simulate bigger gradients and have a lower wattage floor.
While the wattage floor and gradients sounds insignificant for TR, in my experience the Flux was a PITA. It couldn’t control precisely below 150w so in recovery intervals I found myself having to change gears and alter cadence to hold a 40 or 50% recovery interval. Vice Versa, it couldn’t hold max wattage in a low gear so I would then have to change gears up until I found a gear that it would comfortable hold 90-120% intervals.
I’m now hoping tacx will either refund me or replace my flux with a flux s so I can sell it and buy either a kickr or neo 1.