Open Source Android Development Tools

hello.
Is there a summary of where things stand with regards to open source alternatives to Studio? I have found Studio difficult to use, but i understand it is the only way to build signed apps.

I have been trying to cross compile my own open source SDL2 apps for fdroid/Android, so I can use my own prefered IDE to write the app, but I get beaten by the studio tools, even in command line mode. See:

https://forum.f-droid.org/t/sconnex-an-open-source-sdl-game-for-f-droid

Thanks.