Unfortunately on the FM4-176L-S6E2DH nearly all signals are already used. The only and most comfortable chance I see is to use CAN instead of SD card. CAN signals on pin 25 (RX2_1) and pin 26 (TX2_1) are routed to RN23 (series resistance 33 Ohm) and to CN13 (SD card slot). Somehow you can modify the board in this area to connect the external CAN PHY. Be aware of the RN22 (100k pull-up resistors).
Thank you so much Holger Wech for your reply. I now try what you suggested.