Quake Champions is in kind of a strange place right now. It's been publicly available for almost a year, it boasts cutting-edge gib-splosion technology, and it's good. But it's also still in Early Access on Steam, and so even though it's intended to be a free-to-play game, it is not currently free: If you want to get in, you have to pony up for the $30 Champions Pack. Until June 25, however, you do not.
Your response to #Quake has been overwhelming! We want to give latecomers a chance to get in on the action too, so we're extending #F2P access for another week! Play free through Monday, June 25, and stay in! See you in the arena, Quakers! pic.twitter.com/AVZdlDqTVdJune 18, 2018
It's not a free-for-keepsies offer as far as I can tell (the announcement on Steam says Bethesda is "extending free-to-play access until Monday, June 25," which reads to me to mean that access will go away when Monday arrives) but that's not a huge blow since it is, eventually, going to be free anyway. And if you dig it so much that you can't wait to get back to it, the Champions Pack, which includes the full roster of characters (current and future) and other bonuses, is also on sale, going for $20/£13/€20 until June 21.
Take note that the free-to-play offer is applicable only on Steam and not the Bethesda Store, which isn't currently showing a "free" option.