How do I stop data collection and tracking

With iOS 14.6 apps that collect and track data will have to ask for your permission. When that happens, you can "Ask the app not to track".

More details here: link-> If an app asks to track your activity - Apple Support

The data that can be gathered is very limited unless you use apps like Facebook which naturally gather a lot of social interaction data.

You can’t stop commercial apps like Amazon because you volunteer your data in order to buy stuff.

Check in App Store for each app you have installed and see what data is tracked,

To avoid all data mining then sell your smart gadgets.