<snip.. a long boring post about turbos>
If it’s a good price just get that Fluid 2 that woolymonstetr was selling. A pretty decent fluid turbo will do the job nicely.
Though I’d try and get hold of a Kurt Kinetic Road Machine (here) with their InRide gadget. The trainer is a really nice fluid one. You can get a bigger “pro” flywheel for it if you want even more of a “road” feel to it. And the InRide basically does what “virtual power” does (derive a power number from wheel speed) but can be calibrated and will be more accurate.
If you want to play with Zwift and you want a properly Smart trainer (an electronic one that’ll vary the resistance to the terrain of a virtual course) then just get something like a Tacx Vortex Smart.
I’d avoid a mag one. They can be pretty cheap but they feel quite un-natural. You’d notice it if you rode a fluid/air and a mag back to back.
All this is assuming you don’t want to spend too much cash and you don’t have any other specific requirement (e.g. needs to be really quiet, needs to be direct drive, needs to have a super wide resistance range, etc.)
Edit… also if you have knee trouble you might want to factor this into turbo choice. Low inertia ones need a bit more effort pedalling through the dead spots, this might put more of a strain on the knees. A bit like always riding up a slope.