This is one of those things which is dependent on a "network effect" by individual sovereign nations (as well as local subdivisions), carriers and, of course, passengers themselves. If it becomes generally accepted, people will use it. But, to do that, infrastructure will have to be there.

The key is that, just as it has always been, it is 100% on each passenger to assure that they have, in hand, all required documentation for entry and that they have it in a form permitted or required.

The current situation is untenable and a return to "normal" means that a system such as this has to come to pass.