This black border issue around youtube videos might be as simple as that you are in theater mode rather than mini player mode.

I tend to do that now and then, as like, today. LOL

Just click the player icon (third from the right) and make sure it says you are in mini player. The black borders should now be gone.

NOTE: YT seems to remember the last mode as it seems to carry from computer to computer.

Hope that helps.

@andrew84 I've been noticing this little blue line on Youbube videos and at first, thought Uh! oh! My Sony 4K TV LCD is breaking down. LOL
I analyzed the issue as related to Lucid mode.

When I saw your post about 110%, I checked my zoom and sure enough, it was at 110%. I put it back to 100% and the line goes away.

Thanks for that tip. I don't have to worry about the TV anymore. LOL

I'm finding the same thing on all my computers and all my computers are fast!
I notice that when I first launch Opera, it takes several seconds for the Speed Dial page to populate.
It takes so long that it's quicker for me to just click a bookmark.

But Here's The Other Thing ...

Opera is now using crazy amounts of memory!
When I do a fresh launch of Opera, without even going to any site at all, it's taking up almost 400 Meg of memory!

And like right now, I have only YT on one tab and This Page on the other tab.
There's now 17 instances of opera in Processes!
Each sucking up memory for a total of approx.
805,048 Mega Bytes!
That's Almost 1 GIG for 2 tabs!!!!
Insane !

17 processes of Opera for 2 tabs open is crazy.
I hope that the Devs look into memory management and efficiency, because this is now out of control.

As for Extensions, I only have a few that are needed.