Bike attached to TACX flux smart trainer makes a clunking house and chain feels like skipping
I had the same thing. It's the screw on spacer on the axle (cassette side coming loose. Screw it back in again and solved. For me anyway.
Use the spacer on the non-drive side to get the internal distance between your rear stays just right before clamping down the quick release. Mine works loose from time to time and the bike becomes loose. Check it before you ride - it's never worked loose in a single training session for me.
It's not your cassette if the sprockets don't wiggle when you try to move them. It's not the chain unless it's skipping over the sprockets - almost (not entirely) impossible.
I'm disappointed with my Tacx. Blood noise, squeaky, creaky and comes loose.