Don’t let sourdough vs yeast stop you 
Unless otherwise indicated, most starters are half flour and half water, by weight. Simply divide the starter grams in half and add those amounts to the flour and water weights.
This babka:
- 275g flour (2 cups)
- 200g sourdough starter
- 125g milk (1/2 cup)
- 75g plain yogurt (1/4 cup)
- 5g salt (1 tsp)
Becomes this babka:
- 375g flour (between 2 3/4 cups and 3 cups)
- 100g water (0.4 cups…very scant 1/2 cup)
- 125g milk (1/2 cup)
- 75g plain yogurt (1/4 cup)
- 5g salt (1 tsp)
- yeast amount is up to you, see final note
If you don’t have a scale, deal with grams until the last second.
Then divide the flour grams by 130 to get the cups.
375/130=2.88 cups flour
And divide the water grams by 236 to get the cups.
100/236=0.42 cups water
I would use 1/4 tsp of yeast to get a long rise similar to sourdough and have complex flavors, unless I was in a rush, then I’d use 1-2 tsp yeast and expect the dough to double in 1-2 hours.
