A magnetic levitation demo indicates a possible Meissner effect (which is refuted here by this paper), and this is so much easier than a resistance measurement, which is a delicate task and susceptible to experimental errors. So levitation is used as a quick "first check", especially when you don't have a full lab setup to do other tests, which are much more complicated (in addition to a levitation test or a resistance measurement, one can also measure its frequency-dependent magnetic susceptibility curve, temperature-dependent specific heat curve, or its Josephson effect).

One cannot measure superconductivity with an ordinary ohmmeter. Electrodes, wires and the ohmmeter itself are resistive, the meter can never show zero ohms. You need to set an experiment up with a current source and a voltmeter to measure the IV curve across the material [1]. Even then, the voltmeter will never show "zero" volt because of noise, which needs to be minimized in the experiment and removed during post-processing. In this case, sample preparation is also problematic as the synthesized material is not uniform. And your measurement is also expected to be temperature-dependent to show the material's transition to a superconductor. It's more involved than seeing it floating on a magnet, to say the least.

[1] It's basically the same 4-wire Kelvin sensing used by all milli-ohmmeters. But to characterize superconductivity, you need to do even better. https://en.wikipedia.org/wiki/Four-terminal_sensing