@strolf I am trying to do literally the same thing, and my team has had about as much success as you!
In addition to the Waveshare CAN hat, we also attempted to use a simple MCP2515 CAN tranciever board (we have had plenty of success interfacing these with arduinos)
We have also attempted to use an OBDII (UART) CAN tranciever with the pi UART headers with no avail.