> If you want maximum security use an air gapped computer. But that won't let you send messages on the go.
You can, with some inconvenience, use optical diodes to transmit data from a trusted input device to an untrusted network device for transport over tor, and then push the received messages over a second diode to a display device that decrypts the messages, so that even if you receive an exploit/malware, there is no physical connection that allows unencrypted data to be exfiltrated.