A few that work well and are easy to find:
• myNoise: free, ad-free noise generators (rain, brown/white noise, ocean, "Rain on a Tent") with sliders to tune the frequencies. https://mynoise.net/
• Nothing Much Happens: calm bedtime stories by Kathryn Nicolai where, as the name says, nothing much happens. https://www.nothingmuchhappens.com/
• Rainy Mood: one-click rain in the browser. https://www.rainymood.com/
Tip: whatever you pick, use a sleep timer so it fades out instead of playing all night. On Android, AntennaPod (free, open source) has one built in, with a "+ minutes" extend button and an option to stop after the current episode. https://antennapod.org/
Brown noise or steady rain tends to beat stories if your brain likes to follow plots.
