The same happens on the debian side.
Linux Mint MATE, Linux Mint KDE and Debian 11 MATE
installed it from the newest: opera-stable_82.0.4227.23_amd64.deb -file, and updated it.
Unable to minimize from the minimize button in the top right corner of opera, but pressing Opera in the panel of the DE does minimize/maximize it.
Wow. in KDE your fix worked! Thanks. How about Mate and lxqt? how to fix it in those?
Another problem is that opera window doesnt have any border around it. Any ideas how to make it respect window manager settings?
PS. I already reported the minimize bug