Android is open source. Most companies make their own versions of android that include google services and their own apps, theming

You can get a version of android without google services or emulated google services. This will make a lot of apps on the google play store not work, but its better for privacy. These are phone-specific so you may not find a version available/supported for the phone you are using. Examples are graphene os(exclusive to pixel phones), lineageos and /e/os

You can also install linux on your phone, but i dont know much about this