If you are in single-ended mode using RCA termination, then you do not have to worry about a separate ground between phono and linestage. The interconnection does that. However you likely but not always need a separate ground wire between tonearm and phono. It serves to provide earth ground between phono chassis and TT or tonearm. Many but not all dedicated phono ICs provide that ground wire as a separate wire with a forklike connector that goes to the ground lug on your phono stage.
