Okay, for that I would use the Haversine formula. It’s a little easier but potentially a little slower to do this using a formula in Google Sheets. I prefer to code it within Thunkable but it’s quite complex to set up the blocks. I’ve done this for an app that finds the closest air quality sensor to the user.
This topic includes some interesting suggestions and also a link to info about the Haversine formula in my post within that topic: