The rights to Batman: The Telltale Series, Batman: The Enemy Within, Hector: Badge of Carnage, Nelson Tethers: Puzzle Agent, Puzzle Agent 2, and The Wolf Among Us (as well as the publishing rights to RGX Showdown) were acquired by LCG Entertainment with their formation of Telltale 2.0 on August 28, 2019. They later acquired the rights to Tales of Monkey Island on June 26, 2020.
The rights to Telltale's The Walking Dead games were acquired by the creator of The Walking Dead, Skybound. They are now published by Skybound Games, a subsidiary that contracted members of the Telltale staff to finish The Walking Dead: The Final Season from the Telltale 1.0 offices in 2019.
The rights to Tales from the Borderlands were acquired by 2K, the company that holds the rights to the Borderlands franchise.The rights to the Sam & Max games were acquired by Skunkape Games, a company formed by former Telltale 1.0 staff (and the studio that's currently remastering the games).
These games are currently available to purchase (plus Sam & Max Save the World is available to pre-order in its remastered form. Sam & Max Beyond Time and Space Remastered and Sam & Max: The Devil's Playhouse Remastered will be available once Skunkape remasters those as well).
The rest are not available for purchase (although all are available to redownload if you purchased them from GOG.com, Steam, the Telltale Store, PlayStation Store, Microsoft Store, Nintendo e-Shop, etc.). These remaining games presumably remain in rights limbo. We'll keep you updated as (hopefully) more legacy Telltale games become available to purchase again.
Oh, and the CSI games still belong to Ubisoft, but no one cares about those.