> alternate keyboards can steal your password, alternate browsers can have adware / malware, alternate launcher can do many naughty things etc. etc.
It's plausible that Google is done some of these things, like doing some sort of data mining on everything that you type for example (steal your password), and many official google apps have ads if you don't pay them
Definitely. All mobile keyboards become keyloggers if you enable the spellcheck feature or autocomplete / suggestion feature or any AI feature on it (because they need to collect data to "improve service"). Apple also has made changes to its mobile OS when it helps data collection. E.g Allowing messenger apps like WhatsApp to integrate with the Phone app ensures that Apple now knows who you call (voice / video) on WhatsApp.
It's plausible that Google is done some of these things, like doing some sort of data mining on everything that you type for example (steal your password), and many official google apps have ads if you don't pay them