Just one of the problems with trying to make home made baby formula is that newborns need a very specific, narrow balance of electrolytes. They're not nearly as capable of managing fluctuations as even a 6 month old, it's also why they don't recommend giving them more than a few sips of pure water until they're older. The range is narrow enough that even careful measuring isn't going to be reliable enough to be considered "safe". You'll need accurate chemical analysis on the final product to confirm, which you just can't replicate at home.

Plus there's a whole slew of other micronutrients and sterilization concerns to make something that isn't slightly risky. There is no "safe" way through a shortage if you don't have breast milk, only lesser risks. Just necause newborns are fragile as fuck in some ways and the whole period is inherently risky.