If you are willing to give up that easily unfortunately this was not going to work out, there is no nice UI that you can use for these older switches. You will need to change some settings unplug the SFP plugs from your other switch and test it out. Unless you work in that field which most of us do not. It took me 2 months to switch from OPNSense to Mikrotik router as I wanted to route more then 2.5G and instead of building a new server I went for my largest link SFP+.
The reason why people are saying not to do side gig is so that you can learn, and ultimately success and being proud of what you achieve.
What you want to do out of the gate is more advanced then most, what you are looking for is to setup a transit VLAN between your switch and router, your switch becomes the router by setting up routable interfaces and you create a route on the switch for other vlan subnets to pass it to OPNSense and on the OPNSense to pass it to the switch. You will also have to pass the DHCP relay to wherever your server is.
I used this to read up on intervlan routing (InterVLAN Routing) or this (Inter-VLAN Routing Configuration - %%currentyear%% Step-by-Step Tutorial) and while I think its for Cisco you can lookup the keyword commands in the brocade command reference sheet. Keeping router on a stick is probably the easiest option as you can setup your OPNSense vlans on top of the interface and away you go with trunk ports. I would do that FIRST then potentially experimenting with _new_ vlans on different ports so you do not break the internet.
Good luck
The reason why people are saying not to do side gig is so that you can learn, and ultimately success and being proud of what you achieve.
What you want to do out of the gate is more advanced then most, what you are looking for is to setup a transit VLAN between your switch and router, your switch becomes the router by setting up routable interfaces and you create a route on the switch for other vlan subnets to pass it to OPNSense and on the OPNSense to pass it to the switch. You will also have to pass the DHCP relay to wherever your server is.
I used this to read up on intervlan routing (InterVLAN Routing) or this (Inter-VLAN Routing Configuration - %%currentyear%% Step-by-Step Tutorial) and while I think its for Cisco you can lookup the keyword commands in the brocade command reference sheet. Keeping router on a stick is probably the easiest option as you can setup your OPNSense vlans on top of the interface and away you go with trunk ports. I would do that FIRST then potentially experimenting with _new_ vlans on different ports so you do not break the internet.
Good luck