If you're using Onavo, Facebook will continue to operate it for a while (without the data harvesting) to give you time to find a replacement VPN app
"Facebook has also ceased to recruit new users for the Facebook Research app that still runs on Android but was forced off of iOS by Apple after we reported on how it violated Apple’s Enterprise Certificate program for employee-only apps. Existing Facebook Research app studies will continue to run, though.Facebook will shut down its spyware VPN app Onavo | TechCrunch
With the suspicions about tech giants and looming regulation leading to more intense scrutiny of privacy practices, Facebook has decided that giving users a utility like a VPN in exchange for quietly examining their app usage and mobile browsing data isn’t a wise strategy. Instead, it will focus on paid programs where users explicitly understand what privacy they’re giving up for direct financial compensation."