The magic isn't in the device, it's in the flashing and configuring it for non-technical people.
But I think you are missing the point here - people who are asking the questions you are asking aren't my typical customers. It's some random guy who has never heard the word "linux".
But aren't you just selling junky products? That seems pretty unsustainable as well.
Print on demand is just designing your own t-shirts, mugs, shoes, pillows, jewelry, etc through services such as Zazzle, Teespring, Gearbubble. People have passions, such as for animals or hobbies, and love to signal it.
As for sustainability, dropshipping will kill your credibility if you keep doing it. There's plenty of shared warehousing/fulfillment services now like ShipBob where once you've established yourself, you can gradually scale your fulfillment and start wholesaling. I would move away from generic dropshipped products quickly, which are the easiest to start selling, just due to competition. But print on demand and private labeling are solid choices since you own the brand and design.
What is this "brand" that you speak of ? do consumers even care ?
But i don't understand what brand does a store that sells similar stuff to what you can find on Amazon can get.
0. https://nytimes.com/2017/05/03/magazine/the-online-marketpla...
It's better in the long term to set up your own store and build up lifetime value around your own brand, which is what I'm currently doing. You can start out that way dropshipping from AliExpress or with print on demand products. It's more work, but it's also more stable and of course scales a lot better.
But an even better suggestion is to build SaaS products. It scales even more and not many people know how to do it.