The thing is that there is always a bias. An AGI is created by humans and therefore will be imbued by human biases and, if it manages to rewrite itself free of human biases, will create its own. This has already happened with some so-called objective AIs and algorithms, where they show bias against racial minorities etc.
I would suggest you have a look at critical realism. At its core, this perspective states that there is an objective reality that exists, but it will always be perceived and interpreted through different perspectives because conscious entities create their own realities to navigate the world.
Therefore, there might be an objective reality, but its perception is always biased.