So if I buy this but my market has no 3.0 whatever the letters come after then it's no use to get it
Don't bother buying it for now. For one thing, pretty much all manufactures of outboard ATSC 3.0 tuners, were going to release them into what they THOUGHT was a free to air signal. Since the providers have stupidly decided that encryption should be turned on, they've likely halted release. Why bother, because IF they can't handle encryption, people are going to scream bloody murder when they won't work for them. DRM encryption is NOT something that can simply be added later via a download, IF they aren't designed for it from the start (like the HDHR 4k tuners were, so a new download will work with them, ONCE they finally get certified)
So, they now have to redesign, and get certified to handle the new encryption. WHEN or IF that happens, you can be pretty sure they WON'T sell for just $75 anymore.
Besides, ATSC 3.0 Lighthouse setup right now is all a giant beta test, and simply rebroadcast of some .1 channels with barely better specs. There's simply NO real reason to get an ATSC 3.0 tuner right now, UNTIL it's guaranteed AND certified to be able to handle the DRM encryption.