Okay, let's try this again since you gave such a reasonable response.
Let me tell you just a tiny bit about myself; I am a hardcore pragmatist, who's generally never interested in epistemology or metaphysics unless it's absolutely necessary. I'm also a moral relativist and I reject the idea of objective meaning as a concept. This is an important point to me in many different areas, religion, politics, morality, language and so on.
If I didn't think the objective meaning would be problematic as a concept, I probably wouldn't bother talking about it or thinking about it at all. This isn't a discussion about whether we want objective meaning or not - but whether it exists but I think it's important to understand my motivations here. I consider it to be a dreadful thing, when the concept of objective meaning is invoked, I am less concerned by the falseness of the claim but with how this idea threatens many things I hold to be of great value. That's another thread though.
Understanding vs Meaning
Let me clarify my position, understanding requires interpretation or "this means that". Understanding is not the same as meaning but meaning also requires interpretation. To understand language, we need to have some idea of the meaning of words and phrases, obviously, so I'd argue understanding requires meaning and meaning requires interpretation.
My understanding is that your position is that language has a coherent ruleset, the meaning of words is defined in the language and there are correct ways to use the language and incorrect ways. The language no longer requires interpretation,
you simply need to follow the rules.
Now we're talking about language without anyone to speak it, so there's no "you" and the rules will persist regardless of whether or not anyone is there to interpret or use them.
The first really important thing we needed to clarify is what are the actual rules for English you're referring to. I don't think you ever appreciated how big of a hurdle this is. I am going to limit myself to talking about English in a universe where no humans exist so I hope you'll do the same since that's what we're talking about.
Very odd question. I would advise them to learn the language in the usual ways, and use the usual resources, such as a dictionary or a language learning app. We've all learnt a language as children through to adulthood, and that entails learning language rules. A great deal of it is automatic for us, of course. We learnt the rules long ago. You understand what I'm saying without any need to learn the rules. — S
Let me rephrase the question then, in a universe where there is nobody. Where are the rules for English? You're saying English has these rules that will exist regardless of people but I don't know what rules you're talking about. I don't know what you think I'm trying to prove by asking this from you so let me clarify.
My position is that English does have some basic rules, these rules are insufficient to argue for objective meaning, like not even close. They don't even attempt to do that, they are just some basic rules of which half of them a lot of people just ignore anyway. I use Grammarly to help me with my punctuation and half the time I ignore its advice because I disagree with it.
If you want to argue English has rules to an extent that creates objective meaning then you need to clarify what they are. If you take this exercise seriously, I hope this in itself will disprove the idea that English has rules sufficient for objective meaning. If not then, we can continue to debate once we have some rules and talking about what they can and can't do.
It will not be an easy task to show any ruleset you provide is some kind of official ruleset for English. Dictionaries are not the same, common use of English bypasses some of its rules and new words are created, definitions change and the language is not being used the same way by everyone. However, I will not make this an issue, just bring up some rules and we can examine them.
If you can't do this, then at least rephrase your argument. It's preposterous to argue that the rules of English do this or that without even explaining what the rules for English are and just telling me "You know them" when this whole exercise assumes I don't even exist.