@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)
My main point of confusion on the last link is why has Seeed provided a whole page on enabling the spi headers on the Odyssey if they are not available for use? If there are any technicians seeing this, we would really appreciate some input!