Bring on the new post and more details, this stuff is interesting.
PEFT is not for adding knowledge, that's obvious
I get the sense that you want to do the anti-RAG: take some relatively small corpus of data, train a lora, and then magically have a chatbot that knows your stuff...yeah, that will not work.
But chatbots are only one single use-case. And broadly I think this pattern of LLM-as-store-of-knowledge is a bad one (of course, until ASI, and then it isn't).
That said, you absolutely can impart new knowledge through fine-tuning. Millions of tokens is a rather small hurdle to overcome. And if you're not retraining with original/general data, then your model will become very specialized and possibly overfit...which is not an issue in many instances, and may even be desirable.
In a strict sense, finetuning can add new knowledge but for that you need millions of tokens and multiple runs without using LoRA or Peft. For practical purposes, it does not.