I have played with and constructed antenna since I was young from Beverage radio to shortwave, longwave, CB, TV. I have tried so many antennas over time, and so many amplifiers.
So not from an expert view but from experience view my answer to the question how far will a TV antenna get a signal is, it all depends. 40+/- Miles is a good start for an overall answer but it is so much more involved. (Not talking about getting skip signals)
Digital has changed things some. I do not get signals anywhere near as well and far as I did when they were analog. Height of the antenna has always been one of the most important aspects to get signals that are not close, but I find even more so now. Digital is more easily blocked.
Terrain plays a huge role, if you have a direct line of sight you will get a more reliable signal and from a longer distance than if there are trees, mountains etc in the way. Even strong electrical lines very near you or even airplanes going overhead can disrupt a TV signal. There is actually such a thing as a "sweet spot" Sometimes physically moving an antenna just a foot or two one way or the other makes all the difference. I don't mean aiming it I mean aimed the same way but moved over some.
Weather and time of year plays a role. Clear nights can get you signals you may not during the day or in bad weather. And when the leaves are off the trees if you live where they fall off can make a difference.
The type of signal makes a big difference. Hi or low VHF, UHF etc. And then getting the right antenna(s) to match those signals.
Amplifiers are somewhat misunderstood. There are two types or times you might need one. If the cable from the antenna has a long run and/or feeds several TV's you need to boosts those signals.
The second type is the more misunderstood. This one is to get a signal that comes and goes or you can't get at all without it. People will say you can't amplify a signal that does not exist and that is true. There has to be a signal. But what is misunderstood is just because you don't get a channel at all does not mean an amplifier won't bring it in. Or another way to say it, that does mean the signal is not there. The signal may be there but be below the noise floor. It is possible especially a good amplifier mounted at the antenna can make that signal be seen.