If you check out the product mentioned in the summary (Turris Omnia), they call it "open source hardware," but there's no schematic or reference design offered or even promised, they don't mention what if any network ASICs it uses - so how is it "open hardware?" Their previous offering, "Router Turris," despite having a reference design and being claimed as "open source hardware", used the Qualcomm QCA8337N-AL3C, so it isn't really open hardware, either, and is much more closed than hardware which doesn't require binary blobs to work (well). If I document a Juniper SRX in a box with an Arduino connected to its console port, can I then call it "open source hardware?"
Broadcom has the lion's share of the market for network ASICs, and is very much a closed environment. So, there you'd find all sorts of binary blobs. The Soekris' (there are no doubt similar ones from others) are really embedded PCs, with good open source driver support much like a PC. But they provide more ports with lower power, smaller footprint, and lower cost than trying to configure a PC for anything but the simplest routing. Soekris' uses the Intel 82574L Ethernet IC, which is supported by the open source e1000e driver.
It's not clear what the use case is (in the near term) for home routing with multi-GB throughput. Isn't firewall/NAT/VPN the main need, with non-routing/bridging services (DHCP, DNS, print/file sharing etc.) tacked on for convenience since consumers seem to think that "routers" do more than divide broadcast domains.