Modern browsers now apply rel="noopener" behavior automatically to links when target="_blank" is present. However, according to the MDN browser compatability table, Opera still does not do this.
This seems very strange to me, as Opera is based on Chromium, and I would have thought that this sort of update would have been made to Chromium, rather than the proprietary Chrome wrapping around it. Can anyone confirm that Opera DOES NOT apply noopener behavior to target="_blank" automatically? (And even better, why not?)
Update: The compatibility table has now been fixed. Opera has the correct behavior of target="_blank" implies rel="noopener" behavior like all the other modern browsers.
Old answer:
Seems like the compatibility table is wrong about Opera's target="_blank" implies rel="noopener" behavior (it should say "Yes"). There is an open issue about it: https://github.com/mdn/browser-compat-data/issues/17607
According to the reporter, the behavior is present since at least Opera 90.