There are some products similar to the Signalink that provide more connections to the radio. For example, the West Mountain Radio Rigblaster Advantage - with a single USB - provides the audio, CI-V (CAT), RTTY and Key connections.
Otherwise you use the Signalink for audio and a separate serial port for CI-V.
You can use a cheap sound card interface but it will not key the radio via VOX and won’t provide isolation against ground hum. Having said that, I use CI-V commands to key and unkey.
There is some programming software for programming memories. Don’t know if there is software for Linux.