A patent registered by Xiaomi has revealed a modular smartphone concept that consists of three separate modules. It seems Xiaomi is considering hardware costs with this particular design, which would fit nicely into the modern Mi Mix range. Under-display camera technology could also be integrated into this Xiaomi modular phone.
https://www.notebookcheck.net/Xiaomi-considers-hardware-cost-cutting-as-patent-reveals-modular-smartphone-concept-that-would-make-a-great-entry-into-the-progressive-Mi-Mix-line.539757.0.html