I can recommend the rain gauges from Ecowitt, but they need an additional (small) gateway, wit ir without display:
And the needed Misol & Ecowitt Homey app is still very actively maintained by the app developer.
But you could also make your own rain gauge with a door/window sensor. This following video explains how. Unfortunately only in German. But with subtitles in your language, it should still be understandable.
Even if it refers to Home Assistant, it’s possible with a Homey and a few flows and variables. If you want a device to display the amount of rain, you can create a virtual device with the Device Capabilities app.