HI @yoonseok!
The issue arises because the default permissions after mounting the SD card are restrictive (drwx------), allowing access only to the root user. To make the SD card accessible to all users, you need to adjust the permissions and ownership after mounting.
Try changing the ownership of the mounted directory to a specific user or group (e.g., system or media_rw) and modify the permissions to make it accessible to other users
Best Regards!
Chavira