How to solve Error message in Google Sheet array formula: The resulting array was too large

I tried to use this formula below on my Google Sheet for around 10,000 row data:

=ARRAYFORMULA(IF(LEN(L3:L),M3:M&" - "&MMULT((M3:M=TRANSPOSE(M3:M))*(ROW(M3:M)>=TRANSPOSE(ROW(M3:M))),SIGN(ROW(M3:M)))+0,IFERROR(1/0)))

but it came out error message.

"The resulting array was too large"

Can please advice me good solution?