No. Firstly, "USB over RJ45 extender" doesn't mean USB over ethernet. Secondly a print server doesn't connect HID devices like mice or keyboards.
The print server solution is the right track, though. There are adapters that provide a remote USB host interface through an ethernet tunnel for other devices, or virtually any usual USB device.
The access on the PC side is through a virtual USB driver, not specifically an USB port. Respectively any ethernet interface interface can do.