Firefox Relay is open source though, here's the source code: https://github.com/mozilla/fx-private-relay-add-on/
And for the server: https://github.com/mozilla/fx-private-relay/
Also:
While there may not be as many options as for Chromium-based browsers
Many Chromium-based browsers offer no extensions on Android at all?
A place to discuss the news and latest developments on the open-source browser Firefox
Firefox Relay is open source though, here's the source code: https://github.com/mozilla/fx-private-relay-add-on/
And for the server: https://github.com/mozilla/fx-private-relay/
Also:
Many Chromium-based browsers offer no extensions on Android at all?