The AD&D 1e DMG contains everything necessary to play the game solo. It is full of tables that can generate every aspect of the campaign, from the governmental form of a city down to the disposition of an individual NPC. However, it provides the barest guidelines on interacting with all that content, preferring to leave it to the discretion of the DM. A binary question-and-answer oracle could be used to fill in this gap. I find the term "GM emulator" to be a bit misleading, as they don't actually fulfill the function of the GM, which is to play the world in response.
By the book, there's not a whole to do in OSR games beyond traveling into the unknown, encountering monsters or friendly NPCs, engaging in combat, and recovering loot to level up to recover more loot. They really do rely on the strength of the DM to make the game interesting.
When I play RPGs live, I play from the perspective of my character and focus from personal point of view. When I play solo, I feel more like an omnipresent narrator that watches other characters take action as I roll for them.