snip;
"I ultimately got fed up with replacing Kobos and went for an Onyx Boox - Android e-ink with WiFi and a proper touch screen "
Excuse my ignorance but I have never heard of this device. If you could elaborate on it a little it would be helpful. Works as any Android device with WiFi only connection (gps or flight computer) or could it be Bluetooth, "proper touch screen" ?
Looked it up on the internet kind of expensive but if it works???

(Copied from other thread) I'm using the C67ML Carta+

Here's one for sale:
https://www.amazon.com/Android-Scree.../dp/B072LW7DM7

Official specs here, although their base model is now the Carta2:
https://www.boox.com/boox-c67/

I only used WiFi to download XCSoar. In flight it's hard-wired through its USB connection to a IOIO box, but you could use WiFi on a local network. As it uses an Android OS, there is no need to re-flash its firmware.

The Kobo uses an infrared "touch"screen, that side-illuminates the surface of the screen and detects any shadows from your finger. It's a nice idea but can freeze temporarily in strong sunlight (that overwhelms the IR detectors. The Boox uses good ol' capacitive touch instead.

DH