I guess the default one. I haven’t tried the other ones.
The default one is different per operating system or desktop environment. On KDE it's Breeze, on Windows it's Colibre, on macOS it's Sifr (off the top of my head).
I just checked, the one I was using, the default on NixOS with Sway, was Elementary, which I didn't like. I will admit that I liked the other built-in ones better, but I still like OpenOffice's better than any of them.