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Filtering via hosts file requires root, and the author of NetGuard used to approach it that way. But if you don't have root then the VPN route is all that's available. NetGuard uses internal tools to determine which app is the sender of network traffic, and that is what allows for the per app restriction and logging, but this is quite advanced in terms of a VPN app. To be frank, it's not actually a VPN, that is just the only way to modify DNS without rooting a phone.
NetGuard