An audio interface is often required to connect your transceiver to a computer. They are implemented as a sound card device, with various combinations of audio isolation, serial control (with/without isolation), PTT control (with/without isolation), audio level controls, various connections, and other various add-ons.
Some radios don’t need one, and just use a USB cable instead.
S21RC Digital Interface - https://s21rc.net/s21rc-digital-interface-rev-3-0-ham-radio-computer/
All In One Cable - https://github.com/skuep/AIOC
Universal Radio Controller - https://g1lro.uk/ - Based on the AIOC Project
2M0IIG’s board - https://github.com/mpentler/k0rx-interface-pcb
Signalink USB
RIGblaster
Digirig - https://digirig.net/
Xeigu CE-19 (for G90)
MiniProSC - https://www.g4zlp.co.uk/unified/DM_MiniPro_SC.htm