PI-Hole docker on Qnap?

[Enquiries]

Hello, I have huge issue with my Qnap settup. I have TS-251D with single NIC. All manuals over the web are saying to use the container in bridge mode with virtual switch. Since I have only one NIC and if I create a virtual switch, I lost connection to the NAS. Do you know why ? Maybe I need second NIC ? If yes, can I use a cheap usb to Ethernet dongle ? QNAP expansion cards are pretty expensive so can I use 3rth party pcie Lan card ?

Thank you !