I agree, however there are some really responsible companies selling there. For example, JY-MCU, Robodyne, DevEbox, and others. Most of those do supply pinouts and full schematics online, sometimes source code packages as well. When not, they will often supply it to you on purchase. The build quality of the good stuff is equal to the ones you mentioned, and their products reflect extensive R&D, they are not just cloning stuff.
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