So I did this #pinephone mod (https://tuxphones.com/pinephone-storage-performance-pinecil-vccq-emmc-mod/) that was on the HN front page a while ago. The soldering was very difficult for me, so I don't think a newbie should attempt it. After the mod, emmc OSs would often fail to boot, but microSD OSs booted fine and seemed to have no trouble mounting and accessing the emmc. With pmos and the device package mod flashed via pmbootstrap, the phone boots from the emmc fine. Speed "feels" better, but fio results are meh.