Generically speaking everything looks fine.
So GobiSerial does require the usbserial kernel module as well. After copying GobiSerial.ko to /lib/modules/4.19.75-v7+/kernel/drivers/usb/serial/, the developer needs to run “depmod” on the CLI to update the modules dependence. Otherwise modprobe GobiSerial might not load usbserial automatically.
Note: You should do “modprobe usbserial” before manual insert GobiSerial module.
Regards
Matt