Have started to think about packet radio. Question: Will a TNC-X work with a Ten Tec Century 21
Packet radio has died out considerably over the past 5 years. There used to be an extensive VHF packet network back in the 90's. Same for HF packet.
Now not so much.
I would recommend you try the many different digital modes that are being used on HF now. PSK31, JT65, Olivia etc.
However you will need a radio capable of transmitting SSB for those modes. A SignaLink USB interface, computer and software will work for digital modes.