I didn’t know that. I thought they got wiped out with the Temple.
They’re everyplace that there are Jews, as are the Levites. And all the priestly gifts practiced during the time of the Temple still hold, including redeeming our first born, and priestly blessings. But the first fruits and truma offerings are only obligatory in Israel. Levites, however, can receive their tithes, which don’t require ritual purity to eat.
What the Ethiopians did was continue them as a custom in Ethiopia, which was fine in Ethiopia. The problem is that they’re giving first fruits and such to their Cohanim in Israel, which is more than a custom, it is sacred, and no Cohen is presently in a fit state to eat sacred foods at present.
We’d need the ashes of the Red Heiffer for that, and pure red heiffers are few and far between. There’ve only been a few throughout history. Nearly was one a few years ago, but it had a couple of black hairs or something, so it was disqualified. So either we find a pure Red Heiffer, sacrifice it and incinerate it and use its ashes, or we find stored up Red Heiffer ashes at an archaeological dig and use them for the purifications (would have to be in a sealed, specially marked container).
In the interim, no Cohanim should be eating sacred foods, and according to some opinions, the visits to the Temple Mount might even be forbidden, although there are more lenient opinions that people rely on nowadays for that.