There is not a canonical way to perform this, as the Hotspot logic is thought to be applied over WiFi.
Try changing the firewall settings as in the picture and let me know if it works (Default Forwarding Action to Accept for Hotspot). By default router drops the connection from LAN to hotspot and vice versa for security reasons.
And try setting up the IP range of the hotspot to the same range of the LAN.
There are some more advanced configurations you can perform by accessing the device via SSH
And making the changes accordingly to the following link
Of course, we can perform certain changes to the device's Firmware, but for this you should formalize a contact with a teltonika sales manager and provide certain business information of your company that he/she will require.