Animal studies are ethically atrocious and also dumb AF since they can't replicate male pattern baldness. These dickheads should just try it on themselves.
Probably not a good idea (RXShop.md pharmacy editorial team, general information only):
No evidence that stevia improves minoxidil absorption or hair growth.
It can change the product. Minoxidil solutions are balanced for solubility (alcohol, water, propylene glycol). Adding powders or sweeteners can make minoxidil crystallise or settle out, so you get an uneven dose, and sugary residue on the scalp may feed yeast and worsen dandruff or seborrheic dermatitis.
If the goal is to reduce irritation or the sticky feel, the foam version or a propylene-glycol-free formula is the better route. If the goal is better absorption, microneedling (on separate days) has actual evidence.
Generally it is best to use minoxidil as supplied and keep any extras separate.