i want to make the recipe without bacon but i want it to have a complex flavor. any suggestions?

Smoked paprika is a brilliant addition for a greater depth of flavor, without adding bacon or other smoked meats.

Smoked salt ! It gives a nice, smoky earthiness to beans and such. I used some in red beans and rice a while back, and was very impressed. Use a light hand, though. It is VERY potent.

Smoked turkey (whichever parts you choose), is a great option. I don't eat pork, and I have been using smoked turkey for years.

i found smoked turkey parts (necks, backs, wings, butts) in my grocery store and used them recently to make collard greens for someone who doesn't eat pork, which i normally use. they worked great!

Bragg's liquid aminos or a couple of drops of liquid smoke (it's not weird - it's literally liquid smoke) can add complexity. Use mushroom stock instead of veggie broth, as it has a "meatier" flavor.

I'm adding to the fennel seeds: blend the seeds in a grinder with kosher salt, chipoltle peppers, sage. We all have lots of sage to harvest from the garden now and that's the essence of sausage.

I find that fennel seed gives a "meaty" taste to vegetarian recipes.

I agree with AJ, anchovies whole or paste will give off a nutty, non fishy complex taste.

How about a bit of smoked paprika? Add a pinch or two at a time & keep tasting...

An anchovy or two, added and smushed with the back of a spoon, added after the onions have softened a bit + a couple tablespoons of red wine + a teaspoon of molasses. Consider re-hydating a few porcini as well, which you chop fine and add, with the cooking liquid, strained. ;o)