I suppose you are right. In KDE (I have XFCE with Kwin) in Aliya Linux, that is based on Debian Stretch and in KDE Neon (Ubuntu), the menu is quite nice and I can have no border. In Ubuntu with Openbox (Nelum Openbox), also I can un-decorate. In Devuan (Nelum-Dev-1 Testing), it can also un-decorate. If the Ubuntu based distro has Gala Window Manager, it can't. Once there is no border, the minimize and maximize buttons go away. This doesn't happen in Windows 10. Maybe, the Opera devs take heed. I'm now using Opera Beta, for in a few days, it'd become 45 final.

Opera 44.0.2510.1449 on Ubuntu 16.04 Xenial.
Opera acts differently in different ubuntu distros, meaning in one right click on the title bar opens up a menu that has un-decorate, whereas another install doesn't have that. No fall down menu. I have no idea how that happens.

Does any Opera dev reads comments here? If devs don't read, there's no use asking questions.

This is the only app that gets into this kind of problem. When using Edge or Firefox this doesn't happen.

There is no hardware acceleration.

Using normal Opera on a 2 in 1. From time to time Opera goes off, makes the screen black and after few seconds comes back in. At first I thought Windows died, but this happens only when Opera is used. None of the other apps do this. Is there a way to get rid of this problem?
Windows 32bit. Windows 10, fully updated.

The first one has a + sign, that is to add a theme from outside, then there is a white one, and after that there are quite a lot of pictures, 111 of them. Are they installed, or available?

Ok, thanks. There are 20 default themes. Would be nice to have the ability to delete them even.

How to uninstall the theme pictures? There is about 30 of them, but I need only one, so once chosen, the rest can be uninstalled. How to do that? This question is not only for Windows.

Opera 39 opens with a top bar, and there is an option to un-decorate in the drop down menu, but when you restart Opera, the top bar is still there. How to make this un-decorate feature permanent? Distro: Ubuntu 64 bit