There are no default Linux fonts, unless you count console fonts drawn on a framebuffer. Text rendering on Ubuntu looked quite different to that on Fedora last time I looked at both.

When I said "default Linux fonts", I meant font rendering. Whatever you get without a default /etc/fonts/fonts.conf or user fonts.conf file is what I consider "default".

It's a meaningless statement because the Linux kernel does not render fonts or include anything like fonts.conf. Linux distributions are very different in how they configure and patch things like fontconfig/harfbuzz and what version of libraries they ship.