Officially, not possible Splinter Cell: Blacklist on PC without Ubisoft Connect (formerly Uplay)
For those who want to completely remove the launcher requirement, the community often relies on unofficial modifications: Tom Clancy's Splinter Cell Blacklist on Steam splinter cell blacklist without uplay
Before you delete Uplay entirely, there are some downsides to bypassing the launcher: Officially, not possible Splinter Cell: Blacklist on PC