I’m currently building one by myself in Elixir/Phoenix/Liveview/Tailwind using Fly.io for deployment. Elixir has been amazing for more complicated app dev. A lot of previous ruby people there. Liveview gives a React like experience without the extra complexity.
Tesla is great for building api integrations. Knock has a great elixir api for notifications and emails. Telemetry is built into most things. Livebook is Jupiter notebooks but better, great for quick prototyping or doing adhoc data analysis.
You can get most of this from just using https://legendaryframework.org/
Want native apps? LiveView Native is a thing https://native.live/. One app to do it all.