You have electrum on computer already, why having it on phone again. Which means you have one online wallet on two device, this will reduce the security. I will advice you to operate the wallet on one device, operating it on computer is the best.

The little review I know about Samsung Knox is that it is a military defense grade secure system that protects against malware and other things that can lead to attacks. If a malware can disturb the installation of electrum, hope Samsung Knox can not?