I’m going to start a list of SBCs that have 2 or more Gigabit ethernet ports that are available at the time of posting. Please let me know if I should have other data in this list. I am focusing on the ARM and Raspberry Pi style boards, as x86 mini PCs aren’t normally considered SBCs, even if they might technically be.
Orange Pi R1 Plus
Rockchip RK3328 64 bit 4 cores @ 1.5 GHz, 1 GB DDR4
2x GigE (one shared with USB)
Banana Pi BPI-R64
MediaTek MT7622 64 bit dual core @ 1.35 GHz, 1 GB DRR3
4x GigE LAN ports
1x GigE WAN port
NanoPi R4S
Rockchip RK3399 big.LITTLE 2 cores @ 2.0 GHz/4 cores @ 1.5 GHz, 1 GB DDR3 or 4 GB DDR4
2x GigE ports