Any self hosted alternative for Gennially?
Have you tried AlternativeTo?
https://alternativeto.net/software/genially/?platform=self-hosted
E: who is downvoting me and why?
who is downvoting me and why?
You're probably making them feel stupid, people downvote for no good reason. It's a them problem, not a you one; everybody should check AlternativeTo before asking for recommendations.
I had no idea this had a self-hosted platform category. Cool!
https://github.com/slidesk/slidesk