Opera does hide the opr part on certain websites where it's absolutely necessary.
If you start Opera like this (via a command prompt or a shortcut that you modify):
"%localappdata%\Programs\Opera\opera.exe" "--user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36", that should cause Opera to pretend to be Chrome everywhere and might work better than some user-agent extensions. The downside to this way though is that you'll appear as Chrome on Opera's sites too, which can break things with addons.opera.com and store.gx.me/mods for example.