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Free VPN apps on Android–many apps leak your identity, ask for questionable permissions, or track you:
https://www.top10vpn.com/free-vpn-android-app-risk-index/
– tested: 150 free VPN apps with over 260M installs from Google Play Store
– 25% fail to protect user privacy due to DNS and other leaks
– 85% feature excessive permissions or functions with potential for privacy abuses
As recommended by Steve Gibson in SN 698 "Which Mobile VPN Client?":
Use OpenVPN, if possible.