Update:
I found an app, CAN Reader… and when I try to connect with that app, the adapter actually sends messages:
ID 00000000h, DLC 1, message data: FE
I choose the right CAN baudrate, and as USB-baudrate, I choose the proposed 460800 bit/s
But then, the app crashes. I tried it both on the phone and the PI.
I am not sure whether it is the right conclusion, but I would say, the adapter is okay, and I must be doing something else wrong 
Ladies and gentlemen,
There is progress!
Being desperate, I decided to buy the white CAN-Analyzer… because why not 
And suddenly, al the problems disappeared.
So now, the next step: search for a waaaay better thingy than the Raspberry. That is such a hassle… Lineage, OpenGApps…
I am going to research myself, of course… but, if someone could help me: what is the best “easy” Android board at the moment? With easy, I mean: I am not the most stupid guy around, but neither a pro Android programmer… so, making an Android build from scratch is probably too much at the moment. As in: I like to study and learn, but I have to do other stuff as well.
Suggestions are welcome!
And, the conclusion: the white CAN-Analyzer works… and the green one - either mine is somehow wrong, or I am doing it wrong, or it doesn’t work. But the white one worked right away: plug in PC, set the baud rate, plug in RPi, set up, go.
I was impatient and bought myself an Odroid N2.
Install Android
Install GApps
Install RealDash
Use the white CAN-USB
Works right away. 
Using Megasquirt.xml and just testing with CAN-messages from PC on the right addresses.
Now, search for a way to set the resolution to 1920x720
How is this white adapter?
What do you mean?
http://realdash.net/manuals/supported_can_lin_analyzers.php
It is the white one, that I have. Works like a charm
The green-transparent one works with the PC, but I couldn’t get it to work with my portable devices.