There's places like APK mirror or Aurora which will download .apk's from the play store.
The problem with degoogled phones isn't not accessing the google play store, it's not having the confusingly named google play services.
https://en.m.wikipedia.org/wiki/Google_Play_Services
A lot of apps rely on google play services. It mostly depends on how much of google play services an app requires as to whether it'll work on a degoogled phone or not.