A lot of webcomics are isekai, about people from our reality who travels to a fantasy world, some times by means of tensei(reincarnation), but it is not only about this.
The different D&D worlds in the past didn't share the same technologic level, or at least when these were created by the designers, but now the travel between wildspaces is possible, and canon, thanks the updated reedition of Spelljammer.
Shouldn' we talk about the cultural and social impact in a world with the arrival of people who a higher scientific knowledge? It is not only about gunpowder and firearms, but also other ideas. For example a motor in a crossbow to reload itself, or in a war chariot could be the end of chalvary. A drilling machine, even animated only by magic, could be used to destroy doors and walls in castle sieges.
Let's imagine a nurse from New Capena or Neon Dinasty reincarnated into Krynn, Greyhawk or Mystara. All that information about biology would be a true for the medicine deities. A lot of people could be healed without magic, but also new biological weapons could be created by evil cults.
Or the materials from XXI century, for example the graphene, could be crafted by an isekai alchemist. Couldn't it?
Maybe the industrial revolution couldn't start because there isn't enough coal in the mines, and the nature deities wouldn't allowed tree be cut for firewood of steam engines.
Or there is a great taboo about the machines because infernal outsiders could controll these, like Christine, the car from Stelphen King's movie.
And several factions wouldn't allow mankind to become too powerful thanks technology: feys, dragons, giants..
And the risk of the reverse engineering. It can be stolen or copied by the bad guys. Let's imagine goblings and kobolds using machines to take revengue against bigger enemies.
Or the music. Some bard who was a musician or singer in the previous life could play bardcore of famous music. Do you know the movie "Yesterday"?
Or the printer is reinvented to publish more books, but then we would need a way for industrail production of paper.