I thought I remembered initial examples of lutu’lu’ and later examples of tu’lu’ later where lutu’lu’ would have been called for, and when that was pointed out, it just became tu’lu’ by convention, but it’s a very old memory, and I’m not one of the wizards of canon.

I don't think lutu'lu' had been used in a canonical sentence, but Okrand has addressed it.

First, after qep'a' loSDIch, ghunchu'wI' reported that "Robyn Stewart's idea of lutu'lu' as the Klingon version of whom got a nod and an explicit lack of contradiction [from Okrand]. naDev tlhInganpu' lutu'lu' is grammatical, but the lu- is more often left off." (Voragh sent this to the list 12 July 1998.)

In 2014, Okrand gave us most of the rest of the information we needed. See the message here: http://klingon.wiki/En/ThereIs . Instead of who/whom, he compares tu'lu' without lu- to there's referring to plural things that are there. This seems to me a closer comparison, since most people would not think your speech stilted if you say there are things instead of there's things.

-- 
SuStel
http://trimboli.name