Line chart with YTD Years based on Slicer selection

skasu Create a dynamic table for the selected year and the previous year:

YearsTable =
VAR SelectedYear = SELECTEDVALUE('Date'[Year])
RETURN
FILTER(
ADDCOLUMNS(
CALENDAR(DATE(SelectedYear - 1, 1, 1), DATE(SelectedYear, 12, 31)),
"Year", YEAR([Date])
),
[Year] = SelectedYear || [Year] = SelectedYear - 1
)

Set the YearsTable as the data source for your line chart.
Use the Year column from the YearsTable for the X-axis.
Use your measure for YTD counts for the Y-axis.

Create a measure for YTD counts:

DAX
YTDCount =
CALCULATE(
SUM('YourDataTable'[CountColumn]),
DATESYTD('Date'[Date])
)

Add a slicer to your report and set it to filter by the Year column from your Date table.
Ensure that the slicer is affecting the YearsTable and the line chart.