I will give this a try, though it is a bit overwhelming, sorry.
I only need a VLAN on one switch port of the Flint 1. I need the rest of the ports to remain on the upstream subnet. It is very important that this is the setup. I do not need WiFi or anything else, just the one switch port for the VLAN.
Am I making these changes in Luci on the Flint 2? I’m a bit confused, I can’t lie.