Not all apps from Google Play require Google's services. Which don't requires testing, and some times the need or lack thereof doesn't even match what the API says. If something you want is on Google Play, you could for example install Aurora Store, a frontend for Google Play that doesn't require the service, only an in-app login.

APKmirror I can't say how safe is/isn't on a technical level, but personally never had problems with it, nor have I seen people complaining. So possibly another alternative.

Also depending on what you need, you can find on F-Droid, Github, Gitlab, or very sporadically, in commercial platforms like Itchio or (if gaming-related) Humble Bundle.