If you don't mind clutter free, simple presentations, try hack.md or cryptpad. Both supports markdown styled presentations, both are FOSS cloud applications and the format of the presentation is highly portable.
If you want to get really ambitious, try marp framework for presentations - still markdown but on steroids.
I couldn't get into it for the life of me, despite several attempts. I am happy for those who enjoyed it - seems like a chill game.