While I understand people taking a position they believe strongly about, which is admirable, something to consider is that while GrapheneOS might require the one time purchase of a Google product, not doing ensures that data points between you and Google persist.
LineageOS always use multiple Google services while giving them privileged access even if users don't use microG. It would be wrong to imply they don't use Google services. microG is of course an implementation of Google services at the system level.
To clarify further they always use Google services for the following:
°Connectivity checks
°Network time
°Attestation key provisioning
°SUPL
°DNS fallback
°PSDS
°eSIM activation
°and more
ALL enabled by default.
This includes any other OS based on it too.
GrapheneOS doesn't use or provide privileged Google services by default.