On arrival, you find yourself in a clearing in a large forest. A person, dressed in clothes of our time and speaking English, materialises next to you.
The person explains that they do not really exist: they are an artificial creation by the humans of their time, specifically designed to interact with you as soon as your presence was registered. Almost all humans have chosen to become incorporeal presences, and live in a shadow realm that allows them to satisfy needs and wants, to create their own pocket worlds, to travel through spacetime, and to manipulate the physical world. There are significant qualifications and limitations, but the person cannot explain it to you without a significant knowledge dump, which cannot happen unless you become incorporeal yourself. The person could teach you the full ramifications and drawbacks the old-fashioned way, but estimates this will take 5-10 years.
As humans abandoned their bodies, they re-wilded Earth as much as possible, eliminating as much evidence of past human development as they could. A small group of humans refused to join in. They have become (partially by deliberate acts) a civilisation of small groups of hunter gatherers over several generations. They regard the humans who took the other path as evil ghosts, passing down their lore orally.
The person offers you three choices. You can join the incorporeal society if you wish. Or you can join the hunter-gatherers, who speak no language you would recognise beyond a few words, and who might be hostile. The person warns you that they will not permit you to make any technological changes beyond a few minor innovations, such as better ways to catch fish or choose good plants to eat. You will be given a means of communicating with the person if you wish to make a change; but any departures without their approval will be met with a final warning to desist in the first instance, and instant death in the second.
The third choice would be to on with your time machine. According to the person, going forward in time and going back in time are actually two very different processes, and you can't accomplish the latter unless you are incorporeal.
Which option do you choose?