There are no open source versions of android in practice. Android is open source. However, it is designed to enable orphaned proprietary kernels. This is the scheme Google cooked up to leverage the open source Linux kernel to enable theft of ownership and planned obsolescence. If the hardware was fully documented at the bit register level, or the source code for the kernel modules (drivers) that connect the System on Chip and modem to the kernel were properly merged into the mainline kernel, this issue likely would not have happened. If this were the case, these devices would be running open source software. These devices leverage open source software but are entirely proprietary and kept outside of both the community's reach and any true ownership by the end consumer.