OPNSense with 1 Ethernet port? - eviltoast

Hello, I’m sorry if this is a stupid question but I need help, I’m dealing with a client without financial conditions who is on a network with recent constant attacks, the only thing he has available to deal with is a mini pc based on N2808 with 2gb of ram ddr3l and a single Ethernet port. I thought about putting an OPNSense here, but is it possible to have the firewall just be another device connected to the LAN? There are very few local computers so I imagine the traffic won’t be heavy. Is possible something through VLAN or something like that? Thanks in advance