Hi,a small/stable solution is the APU4-series board from PC-Engines.https://www.varia-store.com/en/produkt/51978-pc-engines-apu4d4-system-board-4x-lan-4-gb-ram.htmlWith case, power supply and ssd the hw costs around 200€.Also the qotom-devices sells on aliexpress works fine with opnsense. Search for qotom into forum, will show you many entrys about such devices.best regardsDirk