A wheel on smart trainer is the easiest way to use an old bike on Zwift or similar power output based interface. I use a Wahoo KICKR snap. The doohickey to attach the bike to the trainer is similar to that pictured on the Tackx trainer above, except mine has a little notch to accommodate the QR lever axle. The width is adjustable on mine to accommodate a wide range of OLD.
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N = '96 Colnago C40, '04 Wilier Alpe D'Huez, '10 Colnago EPS, '85 Merckx Pro, '89 Merckx Century, '86 Tommasini Professional, '04 Teschner Aero FX Pro, '05 Alan Carbon Cross, '86 De Rosa Professional, '95 Gios Compact Pro, '95 Carrera Zeus, ‘81 Masi Gran Criterium, ‘81 Merckx Pro, ‘89 Cinelli Supercorsa, ‘83 Bianchi Specialissima, ‘VO Randonneur, Ritchey Breakaway Steel, Rivendell Rambouillet, Heron Randonneur, ‘92 Ciöcc Columbus EL