Create a filter pan with below expression

=aggr(only({<Year = {">=$(=year(today())-1)<=$(=year(today())+1)"}>}Year),Year)

then create a variable  vYear at front end with below expression

=if(GetSelectedCount(Year)=0,year(today()),max(Year))

then you can use below expression in your chart to restrict it default to current year ..based on filter selection it will change.

Count( DISTINCT {$<Year={"$(vYear)"}>}id)