Has anyone tried making sourdough with kefir using flour from unconventional "grains"?

There are “grains” like quinoa or kaniwa, known as Andean pseudocereals, that are gluten-free, and I’m not sure if it’s feasible to use them for baking with sourdough. I’ve tried doing this a couple of times, but I have almost no experience using sourdough to make bread and even less experience using kefir to make sourdough, so I didn’t get good results.
I wanted to use kefir and also kefir grains, because they tend to multiply easily.
Maybe I shouldn’t use only pure quinoa or kaniwa flour, because since they’re gluten-free, they don’t have the same consistency as bread made from wheat flour.
Does anyone have any experience with this?

I have made a quite acceptable gluten-free sourdough starter & bread using our most common gluten-free strong bread flour mix (brand name is Dove Freee). The key factor in that mix is the thickeners to replace the gluten, which is not to everyone's taste: xanthan gum ( https://www.freee-foods.co.uk/product/gluten-free-white-bread-flour-1kg/).

I did a 24 hour cool fermentation.
I enriched the bread with bloomed chia seeds. I moulded it in a bundt cake tin.  It's a stiff batter, not a dough.

So I think what you're proposing should be feasible with time & practice.  But depending on your taste, you might want an alternative thickener to help trap the air for a lighter dough.