nube Hello,
I'm on Solus 4 Mate and Audacity uses FFMPEG out of the box for me.
I strongly suggest you install all of the latest updates to your system, first.
I've managed to export a flac compressed audio data in ogg container but:
VLC player and deadbeef refuse to playback the resulting file and Audacity itself can't import it (!!).
It's a non-standard file.
Why not just using flac compression and flac container? That's an option already present in Audacity export menu.
That would be a standard option that generates a standard file and so hassle free for you 🙂
In the menu File > Export > Export Audio... and in the dialog dropdown choose FLAC Files.
Don't forget to change file extension to .flac in the top of the said export dialog or once exported the file.
Hope the hint is anyhow useful 🙂