Ultimate truth, is something that doesn't change dependent upon who's looking at it.
I think that Ultimate Truth exists, but since humans are finite creatures, and don't live very long, Ultimate Truth is not something that is within our grasp...but we experience and depend on the bits and pieces we do encounter daily.
History is a human thing, limited by our ability to observe and interpret things...so it is not Ultimate Truth. There are things going on, influences, etc, that we don't know about and don't have the perspective to understand.
Philosophy is mental fun, and even a useful pastime, but not quite the "real thing". Truth is in the reality of a thing, the living of life, not in the thinking about and speculating on the living of life. I enjoy discussing philosophy, but I don't mistake it for reality.
Yes, things can be true and yet unprovable, again, because we are finite and short lived, we don't have the ability or resources to put many things to a test, or to go back in time, etc. But really, it doesn't matter, because our being able to prove a thing, doesn't alter whether or not it's true.
For humans, truth is relative to our capabilities to observe, perceive, interpret, and speculate...so for us, it is relative, but it isn't dependent upon us (unless you are in the position that we are the only beings capable of understanding truth so it IS defined by us) It is what it is...whether or not we can perceive or know it, or speculate upon the nature of it.
I look at it this way. Humanity didn't always exist...so clearly these things are NOT dependent upon us. There is reality and truth outside of us.
Truth, may or may not have a relationship to belief..in an ultimate sense...but humans live as if what they believe is true, even when there is evidence that it is not true. Because much of our motivation comes from our own thoughts, etc, we live partly in a world of reality, and partly in a world that is what we believe about reality. Though, in a sense, what we believe has such a powerful influence upon us, it is a reality for us too!
People live and die based on both the internal and external influences...what they believe can become true for them...even when it is not forced upon them by outside reality. But it is not ultimate truth, because it is altered by their perception of it.