Opera Mobile used to be the best browser on Earth for Android devices, but there are more and more complex websites that aren't looking well on it. Especially those with complex figures and graphics.
Some examples:
- https://www.worldometers.info/coronavirus/country/netherlands/
- https://ourworldindata.org/covid-vaccinations
- cognitoforms.com
The letters are flicking, the content is unstable on the screen.
With the Android stock browser everything is fine.
I have a phone with Android 8.1 and the latest Opera Mobile.