You can’t open YaST software whilst you do a zypper operation on the terminal and vice versa. Alo the update checker applet shouldn’t be searching for updates at the same time.
And yes the Teamviewer rpm is unsigned.
I got it installed. I’m a newbie. I had to get the path right and ignore the public key errors. Now it’s installed and working.
TeamViewer RPM is signed by TeamViewer key and this package even adds zypper repository and imports TeamViewer key so it becomes trusted. One may import key before installing the package to avoid warning: