I use rosemary oil. A few drops, massaged into the scalp.
There are reliable studies on the NIH site showing that it works as well as Rogaine.
Do not get it in your eyes. And wash your hands after applying. The smell is strong, but pleasant.
https://my.clevelandclinic.org/podcasts/health-essentials/rosemary-oil-the-secret-ingredient-for-hair-growth-with-shilpi-khetarpal-md