Hosting Flet web apps
Flet apps use WebSockets for real-time partial updates of their UI and sending events back to your program. When choosing a hosting provider for your Flet app you should pay attention to their support of WebSockets. Sometimes WebSockets are not allowed or come as a part of more expensive offering, sometimes there is a proxy that periodically breaks WebSocket connection by a timeout (Flet implements re-connection logic, but it could be unpleasant behavior for users of your app anyway).
Another important factor while choosing a hosting provider for Flet app is latency. Every user action on UI sends a message to Flet app and the app sends updated UI back to user. Make sure your hosting provider has multiple data centers, so you can run your app closer to the majority of your users.
📄️ Fly.io
Fly.io has robust WebSocket support and can deploy your app to a data center that is close to your users. They have very attractive pricing with a generous free tier which allows you to host up to 3 applications for free.
📄️ Replit
Replit is an online IDE and hosting platform for web apps written in any language. Their free tier allows running any number of apps with some performance limitations.
📄️ Self Hosting
Host a Flet app on your own server with NGINX.