Search for camera and peripheral support, as for software support, search models which have open source kernel code and bought alot, they usually have best community support, I'm saying this as current owner of poco x3 pro, and i learned my lesson when i bought redmi note 4 mtk 4/64, they didn't released source code for mtk model, so only way to support it is to make Frankenstein from source code of snapdragon note 4 model, some smartphone kernel code with that mtk cpu support, and cherry pick updates from Linux 3.18 to current, while testing and fixing bugs from one lts version to another till you reach current one