The TP-Link RE550 device is compatible with most Wi-Fi routers and wireless access points, including those that use 5G frequencies for their Internet connection, but not directly with 5G cellular networks. It can amplify and forward the Wi-Fi signals from an existing router or access point, regardless of whether the Internet connection is via a 5G box or another type of Internet connection.

However, it is important to note that the device itself does not establish a direct connection to 5G mobile networks, but merely extends the existing Wi-Fi signals.