Privacy Browser 3.3 introduces the option to select a custom proxy in the format of scheme://host:port as described in the ProxyConfig.Builder documentation. There are two preconfigured options, one for Tor which uses socks://localhost:9050 and a second one for I2P which uses http://localhost:4444.

Selecting the Tor or I2P options produce an error message if the official app for those services is not installed on the device. If you are using a third-party app to pride access to those networks, you should use the custom proxy option.