Dedicated network management switches today are usually 1 GbE Base-T switches. These switches are less expensive than most other networked equipment they are being used to manage. Many 1 GbE Base-T Ethernet switches on the market provide the features needed to make it a viable management switch.
You should select a switch that will provide enough 1 GbE ports to connect to all devices you want to manage in the rack. The Dell EMC PowerSwitch S3048-ON and the Dell EMC PowerSwitch N2048 are two examples of switches that are ideal for OOB management of a single rack. Each is 1-RU with forty-eight 1 GbE Base-T ports for connecting to downstream managed devices, such as switches and servers. The S3048-ON has four 10 GbE SFP+ ports, and the N2048 has two 10 GbE SFP+ ports, for connecting to the upstream management cloud. These switches may be used right out of the box to manage a single rack of equipment.