The most popular Linux distribution for end-users (Ubuntu) comes pre-installed with adware. To be fair, they ask you nicely whether to enable it nowadays, which

The most popular Linux distribution for end-users (Ubuntu) comes pre-installed with adware. To be fair, they ask you nicely whether to enable it nowadays, which makes it a few magnitudes better than most Windows adware. But it's sadly still enough to refute "no bundled adware".