This seems like it might be a good place to ask: does anyone know of a low-cost, readily-available SBC box with built-in dual Ethernet interfaces?

I've been very interested in some of Radxa's boards in the ~$30-70 range, like the E52C [0] and the E20C [1], but they don't have many distributors and seem to have stocking issues [2].

[0] https://radxa.com/products/network-computer/e52c/

[1] https://radxa.com/products/network-computer/e20c/

[2] https://shop.allnetchina.cn/products/radxa-e52c?variant=5034...

If you're okay with used, I got an "industrial" mini PC with loads of connectivity for maybe $125? https://support.onlogic.com/product-documentation/industrial... And there are plenty of configurations at lower prices, as well as many other manufacturers in this space.

Banana Pi makes SBCs with lots of networking ports.

Not sure if this counts as low cost... https://store.minisforum.com/products/minisforum-ms-r1-works...