Try to do this. Click to your name in the upper-right corner, then System Settings.
Find System Info, click it.
On the left now you should have "Default Applications".
Try to set chromium from there.
Try to do this.
Click to your name in the upper-right corner, then System Settings.
Find System Info, click it.
On the left now you should have "Default Applications".
Try to set chromium from there.