The Digi WR21 and WR31 do not have an NTRIP client as such but can be used to stream to the serial port.
An NTRIP client is simply an outbound connection to a NTRIP caster with an identifier at the beginning of the socket connection.
Many companies use these routers as NTRIP clients.
The feature in particular is:
The socket ID would be the headers you send in NTRIP and the "Send serial data only when the match string is present" would match on a line return like /n