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.

Adding to what @auster@thebrainbin.org said: I have installed apps that complain about requiring G-services but then work nicely without. Whatsapp being one iirc.

I use LineageOS without any extra G (big or micro) stuff installed.

And since you're making the switch anyhow you might want to switch to the F-droid appstore as well.

The GrapheneOS app store has a sandboxed version of PlayServices that allows you to selectively deny any and all permissions from it.

Not sure what ROM you're using though