It can be disabled from the App Info, at least on my devices.
Do note that if you disable microG I assume you’ll lose access to the location backends.
One component of microG is something called UnifiedNLP (network location provider). Without that you may only have GPS for location.
Running 1.4 q & r on mata and emerald, respectively.
The Disable button in microG’s App Info is not grayed out like other system apps are.
Mozilla and Nominatum are UnifiedNlp backends. They are not standalone items.
Leave microG be. Don’t use any of the Google stuff. Maybe revoke any permissions you deem unnecessary.
Disable or remove microG. Lose location services. Rely on GPS. Good or bad depending on one’s usage.
Flash UnifiedNlp package. Will/should replace microG. Both use same package name, provides only location services, has only one permission. Package includes a bunch of backends.
Look for MinMicroG-UNLP… package if interested.