Most of the workable plans, such as the MIT prototype, are "maglev on a track in a vacuum tube", rather than the original Musk "flies at a 0.5 to 1.3 mm height on aerodynamic lift" plan. That low flying height would require a really smooth tube, with no millimeter-sized sags in the middle of tube sections. Not impossible, just expensive. The whole point of the Hyperloop system is that that the tube is supposed to be cheap.
Dubai Ports World might build a system between Abu Dhabi and Dubai. The route is flat and empty. and not too long. Dubai already has two monorail systems and a metro rail system, all beautiful and underutilized.[1] It may cost too much, but that probably won't be a problem.
A maglev doesn't need the tube below 200MPH or so. One way to build a useful system might be to run in a vacuum tube for long, straight runs, and switch to open track in congested areas. This would allow bringing the tracks much further into cities. Musk's original plan called for ending the LA-SF system in Fremont, near Tesla's plant.