This scenario feels Waterfall because of the fixed scope of 8 epics and fixed schedule of 10/21/2021 so I wouldn’t say you feeling is off on that point. However, this is very much reality in many contexts therefore I can see some utility in this as a exercise in laying out a strategy or approach.
With that said you may start with working backwards from the release date, then laying out the easy stuff, like sprints and ceremonies. This could provide the base layout to then layer in everything else like capacity and availability. After this it seems like a numbers game… How many hours are available, how many people are available, and how much work needs to be completed.
How much or little can actually be done given the current resources.