It’s like if you imported all modern technology into the past: an iPhone alone would standout in the 50s for example. You have the device in hand but no service (cellphone towers are non existent during that era, nor is the internet & social media) so its functions remain basic (note taking, photos, voice memos) while pretty much all apps won’t function (no phone calls either).
You could record what happened back then via video but you’ll be too late when the internet’s infrastructure comes into fruition, so that “1950s lifestyle video” becomes old fast by the time you returned to the present day, but would you be believed if you said “this is shot in 1956” despite the resolution being in 4K in color or consider it mere fiction even though it is not.
I find it amusing that supposedly a modern smartphone is “useless” because it lacks mobile data. Tech like the iPod and PDA were innovative and changed society. Having a device that functions as a camera, calculator, note taking device, information database, audio recorder and even light source is insane.
Other than that, I think one of the best things to do is to learn how something works, head back in time and invent it. Seems like a good way to get reliable income.
Dude, you need to go and watch Back to the Future again. There are ways to make easy money using time travel - without understanding how complicated technology works, going back in time and trying to replicate it without proper infrastructure.