@ebon-hawk: The issue is already fixed in Opera, but because the issue is with updating and we can't update the affected versions to a version with the fix (because it's the update that won't work), you need to do a manual update.
But only once, because after doing the manual update you'll have a version with the fix.
Hi @spike666, try to update it manually, download and install the package from here - it's already version 76.0.4017.94.
There was a bug with auto update on Mac, after you install the newer version manually, you should be fine next time auto-updating it.
Here is official explanation.
@thelittlebrowserthatcould Who uses many tabs like you realize that highlighting the active tab is very important. From my point of view, Vivaldi has the best alternative to highlight the active tab, using the website's accent color. Opera GX also: the borders around the active tab lead the user's eye to it.