Have you tried a non-stock ROM of Android (AOSP)? These don't come with any of Google's proprietary apps (known as GAPPS - they're optional and can be installed separately). You'll have more luck finding an alternate Android "distribution" that is compatible with your phone as opposed to a non-Android build, unless your phone is widely supported by those projects.
LineageOS is a popular choice - for your phone:
- Info - https://wiki.lineageos.org/devices/h850
- ROM Thread - https://www.cyanogenmods.org/forums/topic/lineage-os-16-for-moto-g5-android-9-0-download-and-install/ (Android 9.0)
There are other ROMs will different goals -- some are heavy on customization and some are focused on privacy. It'll be a matter of time and research to settle on the perfect ROM.
There are other OS's like Firefox OS and Ubuntu Touch, but only the first generation Moto G is supported.