Does this app interfere with Project Fi in any way?
Good question. I'm just another user of Block this, but I think the apk should work with either Wi-Fi or cell connections. And may actually make your connections more secure, as it filters for malware as well as ads. I've not seen nor heard of anyone having issues on Wi-Fi, so give it shot. You may need to temporarily disable "Verify apps" in your Google Security Settings besides enabling "download from unknown sources" in regular security settings. Good luck.