I'm surprised to hear it had no hardcopy owners manual.
I bought a 2021 Ram 2500 and it came with an owners manual.
Vehicles these days have change oil lights and regardless of what a quick lube place tells you I wouldn't ignore the light. And if they did change the oil and put a sticker in the window saying next change due at a certain mileage and it was wrong, perhaps they would have some liability in this.
My truck was built last March and bought in April. It only has 3400 miles so far and I haven't changed the oil yet. I figure I better do it before it's a year old, maybe beginning of March?