Yep, my parents are both Android users and have to ask "where is the home button" when someone passes them an iPhone.
This is actually hilarious because Android had all-screen phones with only virtual buttons long before iPhones did :)
I never use the multitasking stuff. Too confusing. I regard the loss of the single physical home button as a tragedy. One of the best UI elements ever created. Not joking. So simple, imposible to confuse because there’s just one, basically nothing about it that requires training, and it acted as the perfect “oh shit, get me back to something normal!” button for the tech-unsavvy, which is one of the things they most-need in a UI. So good.
Answer: sometimes apps let you swipe right from the left margin, sometimes there may be a left arrow in the upper left, but it may not be visible unless you enable tinted Liquid Glass, but also look in the bottom left, there may be a less-than sign, and some times you have to force-quit the app and restart (like with Libby books borrowed via Kindle…)
That used to drive me nuts especially as they grew the phone to size 5+ inches