@rlevy I have the solution for both environments:
MAC:

1. In Terminal enter: defaults write com.operasoftware.Opera OPDisableAutoUpdate true

Windows:

1. Open command as administrator: winkey+ x then select Command Prompt (Admin)

2. Enter the following:
   setx OPERA_AUTOUPDATE_DISABLED true /m

3. Close Command prompt

4. Open Opera
   enter: opera://about

@sgunhouse Is there a way to stop the update in windows and mac desktop environments? (Systems not in a domain)

HTML Imports has been deprecated in Chrome 80. This impacts Google Polymer 2 sites. Is there a date for deprecation in Opera?