How many rounds in a tournament?

I wanted to confirm this, since back a long time ago (in 2014), I believe the interface said something about qualified places on the page of Swiss tournament. I even asked about what this phrase meant back then:

However, now the page for a Swiss tournament does not mention anything about “qualified places”, so I wasn’t sure if the concept was done away with or just no longer displayed on the page.

So, once a Swiss tournament starts, is the number of rounds fixed (computed from the number of players that started the tournament)? Or does the number of remaining rounds get adjusted if players leave?