decent NUCs are much pricier than old discarded hardware

This can be true for some, but for a lot of labbers the increased energy cost of enterprise hardware will exceed the cost difference of the NUC over the expected life of the equipment. That doesn’t mean it’s an obvious choice to go the other way; it’s just something you should consider.

Used on eBay and flashed with the Unleashed firmware. It’s the same price range as Ubiquiti stuff.

Ruckus APs with wired backhaul OpnSense box runs the network.