Turris Omnia is powerful SOHO router. It is based on Marvel Armada 385 CPU - dual-core armv7 running at 1.6 GHz. Current version has two gigs of RAM. It uses as main storage 8 GB eMMC. For 5GHz AC WiFi connectivity, it contains Compex WLE900VX card based on Qualcomm Atheros QCA988x chipset (ath10k). To provide access to older devices capable only of 2,4 GHz it is also equipped with Compex WLE200N2 card based on Qualcomm Atheros AR9287 (ath9k). Both cards are placed in miniPCIe slots to be easily replaceable.
During the course of history it was possible to buy Turris Omnia with just one gig of RAM and also without WiFi.
Turris Omnia has three physical Ethernet ports. One of them (eth2) is dedicated as WAN and connected directly to WAN port. That can be either metallic or SFP. If you plug in SFP module, the metallic port will get disconnected. If you unplug the module, metallic port will be functional again. In Turris OS 3.X this can be done at runtime, on newer version changing the configuration requires reboot.
In Turris OS 3.X the names of the eth1 and eth2 interfaces were reversed. So in Turris OS 3.X, eth1 was the one connected to WAN. We had to rename them in Turris OS 4 due to fixes in vanilla kernel.
The remaining two ports are connected to a fully manageable switch as shown on the picture below.
GPIO and friends
Turris Omnia sold currently in retail and all Omnias sold via Indiegogo campaign contain extension header providing various embedded buses. There was a brief period of time, when connectors for those were not equipped. If you bought Omnia without the header, extending it is much more complex task than just adding the header.