You need to tell which version, from where you did install. Tried to recreate your issue but Veracrypt just opens fine.
veracrypt-1.26.20-1.x86_64 downloaded from VeraCrypt - Free Open source disk encryption with strong security for the Paranoid
From where did you download? The package libgthread-2_0-0 is available in the openSUSE Leap OSS/update-SLE repository. Simply sudo zypper in libgthread-2_0-0