I have a table with 3 columns of data A,B,C.
On column D I'm trying to use TEXTJOIN that ignore blanks (Columns B and C may be blanks) + unique values meaning no value from the 3 results that were joined is the same.
Use:
=TEXTJOIN(",",TRUE,UNIQUE(FILTER($F$2:$F$4,ISNUMBER(MATCH($E$2:$E$4,A2:C2,0)),"")))