Where in 2022 can you get *decent* square drive belts (CD tray)? Not these 1x1mm things.

...if you want a load of rubbish belts. On the other hand, if you want the unit to work properly don't bother with Ali... I have bags full of Ali Express belts given to me by clients who thought they were being helpful by saving me the bother of sourcing parts for their repairs. IME they are worse than useless.
The optimum angle between the pulley sides for grip is different for an o-ring than for a square section belt. The angle of the 'V' for a square section belt is 90º, whereas for an o-ring drive the optimum is <90º depending on the material the o-ring is made out of. A square section belt in an o-ring pulley will 'pinch' as it runs through the pulley, generating high frequency noise in the belt, whereas an o-ring in a pulley meant for a square section belt will not be able to transfer as much torque as the correct pulley. Stretching the o-ring to increase grip puts more lateral load on the pulley bearing, which leads to increased bearing wear.

For critical applications (e.g. turntable motor pulley) o-rings and square section belts are not interchangeable without some degradation in performance. In other applications YMMV.