Anytype is a great alternative. You can use it in its simple form or design your own workflows with custom document types and properties. In Notion everything is a page but in Anytype you can define document types like Research Note, Concept, Bug Report,.. to distinguish between the various types of pages we typically use to organize information in a space. It's also fully e2e encrypted so you do not have to worry about them using your information to train models. It supports multiple devices and can sync between them p2p while maintaining a hosted server copy but does not have a webapp.
