I currently have OPNSense running on a small x86 box, it's sitting inside my network though and providing a secondary network for access to some buddies for "SaaS" I run from home for our projects.
I really want a PCEngines APU specifically for my edge router though, mainly for coreboot and potentially failover to cellular, and it fits nicely in 1u too.
The current goto is commercial display PCs with multiple NICs otherwise there are some great micro PCs e.g. Qotom.