Well, then let me describe what I’ve done excatly:
For starters I am using the latest Klipper version (0.11.0-40)
MKS SKIPR
This is the configuration of the MKS SKIPR accordingly to their Wiki:
Compiled als flashed, it gets recognized as a CAN node and inserted into the printer.cfg
the board gets recognized and is working.
Update: I forgot to mention that I use an external USB cable to connect the STM part to the PI part, because it seems that CAN bridging does not work when using the internal UART connection.
Toolhead:
This is the configuration of the Mellow Fly SB2040 Toolhead board:
all settings accordingly to the Wiki page from Mellow: 固件烧录 (klipper.cn)
CAN termination jumper set with 120ohms as required. But after flashing I get no CAN-ID on the Linux:
Error on Klipper:
MKS PI
CAN-Settings on the PI:
Cable connections:
From the SB2040 the CAN-L and CAN-H
go to the corresponding CAN-L and CAN-H on the SKIPR board:

GPIO-Pins set with these diagrams in the configuration files before flashing
So this is all pretty straight forward (well, once you get your head around how everything’s interconnected here), so i belive there is not an configuration error, but i’d love to be proven wrong