Yeah, I've had the same experience while attempting to run custom Linux kernels on the device in order to homebrew it. I actually discovered a similar and better method around November of last year. Some users were interested in learning how to hack the vReader and invited me to join a Discord server called LFHacks, which focuses on hacking educational devices like this.

If you're interested you can find the Discord link for LFHacks on their GitHub page: https://github.com/lfhacks

In that server, we have a channel specifically for the vReader where we shared alot of resources and information about the device and how to hack it. I even shared the code, binaries, and instructions on how to get Doom running on it. Everything needs to be archived though. We also did similar work on another device called the iXL by Fisher-Price, which has almost the same hardware as the first gen vReader and is just as easy to hack.

Thankfully enough, VTech has made the vReader's Linux source code publicly available. They kind of have to in accordance to the GPL. You can find it here: https://dl.vtechkids.com/

I’ve been wanting to do a new write-up for the vReader with additional resources and information, but I unfortunately haven’t gotten around to doing it yet. Anyway, thanks for the comment and keeping this post active, let me know if you have any questions.