Hi! We have been trying to achieve this task for a week now, and this forum post is kind of my last hope… Since I am pretty new to networking as a coder it might seem like an easy to answer question but consider that I most likely need explanations like I am 10 
In our lab we have a Turris Omnia router together with a switch that has no console access but it does have VLAN capabilities. The switch is connected to the LAN4 port, uplink is on the standard WAN port.
We managed to get the switch to have it’s own subnet and DHCP scope which wasn’t hard but it’s a start to get to know the router and it’s software (LuCI for sure / OpenWRT I think it was called).
Our goal now is to assign every port on the external 24-port switch to a subnet. We tried using VLAN with the default annotation so LAN4.5 was a test interface which would, as I understood, mean VLAN 5 on port LAN4. But tagging port 5 on the switch as VLAN 5 didn’t trigger any positive reactions.
Now my question is: Have you guys ever done this? How would I go about solving it?
Do you know any resources online for this exact case?
I think it is called router on a stick but most guides I found were cisco related which doesn’t really help me understand it.
Best to you all
Sandro