I was sure I had posted about this bug, maybe about a year ago, but a search of the old and new PLUG Forum postings, did not show anything.
I have ran into this issue before and again just now, when setting up a new install of the latest 18.04 Lubuntu, after installing the Opera browser, by downloading from the Opera web site, Opera would only start with smaller window, which I then had to maximize. A real pain in the butt!
I installed the Synaptic software installer, but Opera was not available in Synaptic, so that is why I had to download Opera from their website.
After Googling the issue, it turns out to be a common issue.
The solution from one of the help forums and the one that worked for me was to right click on the Opera icon in the Lubuntu menu, Internet folder and select preferences.
The box that comes up has the command that is being used to start Opera.
You edit the command as follows:
If you open the launchers and change the command from "opera %U" to "opera %U --start-maximized", then it opens mid-size at first, then jumps to maximize.
Cool tip. Thanks for sharing. Is this an issue specific to Lubuntu or did you notice it with other desktop environments?
I believe the issue occured with Linux Mint about a year or so ago.