There are 2 kinds of uses for this. Those that require a very small computer and those that require a very cheap computer. You can buy 4 or 5 Radxa X4 for the

There are 2 kinds of uses for this. Those that require a very small computer and those that require a very cheap computer. You can buy 4 or 5 Radxa X4 for the money that would be used for one NUC-like small computer with an AMD CPU or with an Intel Core CPU. Radxa X4 is much slower, but there are applications for which it is good enough, so there is no need for a more expensive computer. For example I would use it to replace an old Intel NUC that I am using (together with several USB Ethernet interfaces) as router/firewall/DNS server/DNS proxy/e-mail server/Web server/NTP server etc. Radxa X4 would be good enough to ensure the routing and filtering for four 2.5 Gb/s Ethernet ports, while cheaper devices like those using quadruple Cortex-A55 cores are not good enough. For that Internet gateway, which must work 24/7 without downtime, I keep a spare unit ready to replace the main unit, if necessary. That means a double cost. With Radxa X4, the cost for two units remains very small, which is an incentive for using it instead of a more expensive SFF computer. The alternatives at the same price, i.e. Rasberry Pi and the similar SBCs that use RK3588, have a much lower peripheral throughput aggregated over all their peripheral interfaces than Radxa X4. With external USB hubs, Radxa X4 could be extended to 8 full-speed 2.5 Gb/s ports or more, or I could use up to three 10 Gb/s Ethernet ports instead of the 2.5 Gb/s Ethernet ports. The small size of Radxa X4 would be handy if I would use it as a portable firewall for a laptop. Unfortunately the modern laptops cannot be trusted due to the hardware backdoors that are implemented in them for remote management. So a paranoid user would want to disconnect the internal antennas and connect to wired or wireless networks through an external firewall, for which a Radxa X4, which has a published schematic, would be a good choice.