Opera does have a link at the bottom of their "Opera for Androiid" page, which links to

https://www.opera.com/download/get/?partner=www&product=android&utm_source=(direct)_opera_com&utm_medium=doc&utm_campaign=(direct)_via_opera_com

As I'm currently running Windows, I didn't go farther than that. And yes, I did say "the bottom of the page", just below the lower Get it on GooglePlay button. Mind, not sure what you'll need to do on your device to actually install it - on my tablet I have previously had to enable a flag in Android's Developer settings to allow non-GooglePlay installs.