I recently unstalled and reinstalled Opera trying to clear up some problems, but now my old Opera 12 is the only option Windows Settings gives me for a default browser (other than Microsoft Edge). Is there a way to force recognition of the newer Opera other than uninstalling my old Opera 12?

If you really don't want the new start page and don't want to deal with the flip flop option in the lower right corner, go to opera://flags and disable the experimental start page. Even choosing to go back to the speed dial in the lower right corner does not change the default flag setting.

After enabling the proprietary media flag, I had to close and reopen the browser, and then I could hear the Amazon music samples.

I have the latest version of Opera and have the same problem, i.e., Amazon.com music samples do not play. I tried enabling the proprietary media flag, but that did not help.