I’ve got a number of these switches in use. They are quite handy as they do not require external power when PoE is available, and have some nice monitoring features.
For a project, I needed to control a non-connected device in a location where I only had the switch and some other closed devices. My first thought was to try to use the switch to talk to a small microcontroller that could drive GPIO lines as required (this way I would not need to take up an ethernet port)
That idea hit a dead end, but I found some interesting undocumented things on the switch, not just on the serial port but on the network as well.