Rack of Lambda

As a generalized function, perhaps something along these lines:

PMTSUMMARY = LAMBDA(array,start_date,end_date,[interval],[int_type],
    LET(
        interval, IF(ISOMITTED(interval), 1, interval),
        int_type, IF(ISOMITTED(int_type), 2, int_type),
        a, IF(ISOMITTED(array), SEQUENCE(ROWS(start_date)), array),
        n, IF(int_type = 1, end_date - start_date, (YEAR(end_date) - YEAR(start_date)) * 12 + MONTH(end_date) - MONTH(start_date)),
        m, SEQUENCE(, AGGREGATE(14, 6, QUOTIENT(n, +interval), 1) + 1, 0) * IFS(interval > 0, interval),
        j, CHOOSE(int_type, start_date + m, EDATE(+start_date, m), EOMONTH(+start_date, m)),
        t, end_date >= j,
        λ, LAMBDA(x, TOCOL(IFS(t, x), 2)),
        HSTACK(IF(COLUMNS(a) = 1, λ(a), CHOOSEROWS(a, λ(SEQUENCE(ROWS(a))))), λ(j))
    )
)

[interval] (optional) - the number of intervals between payments (default is 1)

[int_type] (integer, optional) - specifies the interval type

• 1 - Days
• 2 - Months (default)
• 3 - Month Ends

See attached examples...