So I study beer and brewing, previously as a profession but nowadays more as a hobby. I've even managed to answer a question in this sub before, which was very satisfying!
In the field, a lot of people are familiar with the story of how the stereotypical figure of the witch came through the male-dominated clergy and other parties interested in seizing beer production for themselves associating alewives with the devil and evil magic.. It's a mundane, typical story of social segregation through the use of spirituality, and it seems generally accepted to be true. The association between witches and brooms would thus come from the sensible fact that brewing involves a lot of grain and dust, so alewives would always have a broom around.
Just saw someone on reddit link this article however, and this one, weirdly enough from the same website as the other one I linked, claims that women would rub hallucinogens on brooms then shove them up their genitalia to get high, and that is how the association between witches and brooms came about.
Of course, one theory does not contradict the other per se, but one feels far fetched to me. Is there any credible evidence of the practice of using brooms for recreational drug use in any moment in history?
e: the links I posted aren't meant as sources of any kind, just illustrations of both theories
There's always more to add, but this is addressed by u/sunagainstgold here: Is there any evidence that medieval women used broomsticks to rub hallucinogens into their vaginas?
And also a bit at the end of this answer by u/idjet: Where do the stereotypes of witch's outfit (conical witch hat, black attire, etc) and witch's broom come from?