I searched the forums but didn't find anything useful so I looked for addresses in Cheat Engine.
(Unknown initial value, unchanged value, changed value, etc. while changing the aspect ratio options, and unpausing to let the game refresh the aspect ratio.)
By nop'ing writes to these addresses you can use custom aspect ratios.
I don't actually have an ultrawide monitor. I just made it some random super wide aspect ratio and resized it from 1920x1080 as an example.
Problem is nop'ing writes can partially break rendering. The character you play as becomes invisible, and the lighting flickers in certain places.
Maybe the exe could be hex-edited instead, or something to prevent that. (But again, I'm not sure)
Also I don't know how to precisely calculate aspect ratio values.
A fix for the 16:10 text in this game, eyefinity/surround in Lego Star Wars III, and an AR hack for Lego Star Wars II: The Original Trilogy might also be possible, but since I don't have LSW2 or 3 I can't test that.
I think someone more experienced could help make this into a fully working hack.
I've provided a cheat table for the Steam version as an attachment.
Most of the addresses have a description.
I recommend using DxWnd to play it in a window as it makes switching between CE and the game faster, and lets you see it even when it's not the active application.
To prevent objects from getting cut-off you must also increase the culling width address, and as explained before you need to nop anything in Advanced Options except "NOP to freeze camera" you can ignore that.