Serials
Kindle Vella is Amazon's attempt at a serialized platform. I have several serials available there, but also on Laterpress and Neovel. Vella is the best option for me at the moment, but the other two benefit readers more.
I personally recommend Neovel (both in design and accessibility), although releases are currently a month behind. I actually publish newer episodes to Laterpress as I write them, so that's the better option if you'd rather not wait a week or more for updates.
Ongoing Series:

Jello On the Wall, a cooking based portal fantasy; chefs are transported into another world and must feed monstrous teens to survive.

Last Train Home, a lighthearted portal fantasy about an aspiring mage trying to find their place in the strange new world of Glasend. Can also be found on Neovel & Laterpress.

The Threads That Weave, dark fantasy and comedy—A mage and monster con team are confronted by the infestation and ensuing chaos they cause. Can also be found on Laterpress.