Manually create A/B partitions I have an Xiaomi Mi 6X which is the Chinese version of A2. There is a way to convert it into A2, but OTA updates won't work because 6X has only A partition. I'm not sure, but I've read, it is possible to create/delete partitions on an Android device.

So I want to create A/B partitions manually, but I have no idea how it looks like.
Android uses GUID Partition Table (GPT) as its partitioning system which is possible to modify using tools like parted and gdisk. But there are a few constraints I can think of, other than the OTA problem you have already mentioned:


Android devices with A/B partition scheme have many partitions in (_a/_b) pairs including system, vendor, aboot, sbl and modem. New partitions require space which obviously isn't available on flash memory (eMMC) and needs to be freed from your userdata partition. So you will get short on your /sdcard space.
Since all the partitions to be created aren't adjacent to userdata partition (which is usually the last one), you may need to delete and create dozens of partitions. Exact details depend on the order of partitions in your partition table. So there are bright chances of bricking your device. :)
Application bootloader (aboot) on A/B devices is different than on non-A/B devices. On A/B devices, there are two boot partitions and no recovery partition. So the process of making choice from where to boot the device is different than on non-A/B devices.
Also the other functionality of aboot that depends on partition names such as fastboot update will also break. And since bootloaders are closed source, you can't modify it to be compatible with your new partition table (unless you are lucky as well as an expert at hexediting binaries).


So it seems practically impossible to convert a non-A/B device to A/B device.