Show dynamic months on the visuals when user is using a single slicer selection

Follow the steps in https://www.sqlbi.com/articles/show-previous-6-months-of-data-from-single-slicer-selection/ to set up the Previous Dates table and the relationship. Instead of the calculation item in the article, create a calculation item like

End of last 3 years =
VAR CurrentDate =
    MAX ( 'Date'[Date] )
VAR CurrentYear =
    YEAR ( CurrentDate )
VAR CurrentMonth =
    DATESMTD ( 'Date'[Date] )
VAR Dec1 =
    CALCULATETABLE (
        DATESMTD ( 'Date'[Date] ),
        TREATAS ( { DATE ( CurrentYear - 1, 12, 31 ) }, 'Date'[Date] )
    )
VAR Dec2 =
    CALCULATETABLE (
        DATESMTD ( 'Date'[Date] ),
        TREATAS ( { DATE ( CurrentYear - 2, 12, 31 ) }, 'Date'[Date] )
    )
VAR Dec3 =
    CALCULATETABLE (
        DATESMTD ( 'Date'[Date] ),
        TREATAS ( { DATE ( CurrentYear - 3, 12, 31 ) }, 'Date'[Date] )
    )
VAR PreviousDates =
    TREATAS ( UNION ( CurrentMonth, Dec1, Dec2, Dec3 ), 'Previous Dates'[Date] )
VAR Result =
    CALCULATE (
        SELECTEDMEASURE (),
        REMOVEFILTERS ( 'Date' ),
        KEEPFILTERS ( PreviousDates ),
        USERELATIONSHIP ( 'Previous Date'[Date], 'Date'[Date] )
    )
RETURN
    Result

Apply that calculation item as a filter on the visuals you want.