Or connect an 8-port managed switch to green and configure ports 6,7,8 vlan to other networks.
Assuming green is 192.168.1.1/24 make 3 VLAN on ipfire and on the managed switch
ports 1-5 green
port 6 - VLAN10 192.168.10.1/24
port 7 - VLAN20 192.168.20.1/24
port 8 - VLAN30 192.168.30.1/24
Can you clarify 3 different “green networks” ?
Do you need for each Green interface a different ip-range(subnet), or do you want to spread on single subnet-range over all 3 green interfaces?
If its the last one, you could easily do this with the “Zone Configuration” in the “Network” section.
Im not an expert on networks…but i gues the first one ( different ranges). Because if all the green network are located at same range…then it has no sense to create 3 interfaces, you can easily put a switch if they are located in different rooms for example…but logically all three would be in the same network…