I want to: Keep sidebar hidden and not use any messengers.

From time to time they come back and enable themselves and unhide the sidebar. This is very annoying behavior. How can one prevent any messenger from reenabeling itself and unhide the sidebar?

I tried the suggestions from this thread: https://forums.opera.com/topic/40897/how-can-i-get-rid-of-the-sidebar
No idea if it is working or not, at least it did not show within 3 days or so...

I want to: Keep sidebar hidden and not use any messengers.

From time to time they come back and enable themselves and unhide the sidebar. This is very annoying behavior. How can one prevent any messenger from reenabeling itself and unhide the sidebar?