I don't think that the concept of relative truth makes any sense. I think all truth is absolute.
I don't think lies are anything metaphysically fundamental. I think that lies are *ethically* fundamental. Although, they're not the most ethically fundamental thing. To me the most ethically fundamental thing is that suffering is essentially bad.
I agree absolute truth is very fundamental. But I see 'absolute truth' as just synonymous with plain old 'truth'.
I think believing in subjective truth is deeply confused.
Relative truth ..... well, I can only make sense of it if it refers to truths relative to whatever those truths refer to. But that even applies to absolute truth and I think that's a completely trivial sense of relative. So, again, I don't think that there's any meaningful way in which truth is relative. So I'm just going to go ahead and say truth is necessarily absolute. Otherwise I'm referring to something meaningless and thereby not really referring to anything at all.
So, I think truth is absolute. But I don't think it's the most fundamental truth that truth is absolute. I think that existence exists is at least as fundamental. I think that consciousness is real is at least as fundamental. There are a few fundamentals. I don't think it's three. I think that there are many fundamental expressions that we can't really specifically innumerate because there are many ways to put things. But there are certainly ways to put things that are incoherent or meaningless. And I don't think that incoherent or meaningless truths belong in the category of the most fundamental truths of existence.