LAB serum without dairy?

Must we use dairy to propagate the LAB?
I understand that mere sugar water would not be good feed, and I think the idea is to use milk in order to give the LAB an advantage over all other beasties.
What about using whole foods, cooked, to offer better nutrition and eliminate competition?
Could we use more rice wash, cook/pureed rice, pasteurized weed juices ,  steamed potatoes,  pasta water, cabbage soup , old beer, flour slurry or other such feedstock?
I ask because I get/have a lot of that stuff, but very little in the way of surplus  milk comes my way.
I can  get old bananas  almost anytime, more than my chooks can eat.
Would a cooled pot of boiled banana soup be a suitable substrate for growing LAB?

I tried rice water and potato water (separately) and both worked. Try what you think will work and see. I can't imagine that anything with a lot of sugar (bananas) would work well, as it would tend to ferment to alcohol.

I have heard the nut milks work...

it's become fairly trendy to brew intentionally sour beers by innoculating the wort with lactobaccillus.  It feeds on the sugars from the grain (malted barley and/or wheat).  I have had success with a single capsule of Swanson lacto probiotics to get the culture started.  

https://byo.com/article/brewing-with-lactobacillus/