I think you are following the installation guide for Oneplus6(t), which has some differences on partitions. I suggest you unbricking the devices using EDL mode. Then reflash TWRP and retry. You’d better understand every steps before continuing. For instance, userdata partition can have a different number and you must be aware of that!
Yeah, I just realize my mistake
Btw will UBL help?
Since it’s UBL and so far there is no way to enter EDL mode even by shorting the connector for Mix 3, as far I know
i have destroyed my Mix 3 5G too when i follow the Guide for OnePlus long time ago.
You can’t boot in EDL Mode because when you format the partitions you erased the information who the phone needed to go into EDL Mode.
Thats why my Mix 3 gets replaced with the Mix 4.
When i can fix my Mix 3 5G, please help me.
I think you can only let the UFS-Memory flash to stock partitions