The product is a manually configured Orange Pi device. Someone made and configured it. You hope that they knew what they were doing and that they did not install backdoors.
With commercial products, you have a base level of communal trust that everyone is trusting the manufacturer and if the vendor did something wrong (intentionally or by accident) then everyone is in trouble. It is bad PR and the company is harmed.
With an individual custom-crafting these devices, you do not even have this level of basic trust. You have no idea if the device has been tested or even if it does what it says it can do. They could install blatant backdoors and if people found out, what could they do? Go to the media? No, they would give a bad eBay review. Then the vendor changes names. You have 0 protection here.
How you trust falls under 4 categories:
- 3rd party review and audit (this is where open source can be handy)
- "herd immunity" where the device is so common that problems would likely have been encountered and publicised or fixed (or if a problem occurs, everyone is affected equally) (also an element of open source code that everyone uses)
- commercial or reputational impact where problems are not in the vendor's best interest
- perform an audit yourself
So, unless you can perform an audit of this device, you are left without a lot of options that you can trust from a random eBay vendor.
But hey, the vendor has 74 positive reviews, it's homemade, and their website is a free dynamic website that could be anywhere and owned by anyone and you have no way of validating the ower of the site. What's the worst that could happen ... ?