I am looking for a tablet that can run a standard mainline blob-free Linux kernel, and has open firmwares/drivers for the at least the DMA-capable built-in peripherals.

The bootloader must be open-source, permit Boot from Flash, SD-Card, and USB, ideally also PXE (over USB-ETH). and (re-)lockable.

I know, this imposes some restrictions like no phablets, and no Intel/AMD gear. ARM TrustZone user-configurable would be great. AFAICT, when it comes to WIFI, my only choice is Atheros (Are they really blob-free, open-firmware?), or USB-WIFI. I'd rather have no built-in radio interface than closed firmware/drivers for one of them.

I wont play games on this, but I still want graphics card/driver combo available, that can display a decent full-screen full-hd browsing session with a dozen tabs of SE, and the odd YT-vid.

Virtualization-capable 64Bit CPU would be great, but I can live with "only" connecting to my remote Hypervisors from this device.

It doesn't have to be ultra-slim, or powerful with 8+ Cores. USB PortS though I require, at least 2. One hast to be OTG-capable. And some way to output HDMI1.4+ while still capable of OTG, and charging. Memory ideally 2GB+.

A solution could be an Android tablet, modified to run without "problematic" hardware/software, augmented with a better U-Boot, reflashed to run a mainline Linux kernel with some standard distro. But then which one?

Market Availability 2016Q3+ at global Internet retailers. Does it exist?