You didn't specify which DM you're using,
(I'm using Tumbleweed with KDE Plasma)
But here's a real-world sample showing how to apply the "no update" argument, using KDE Plasma DM.
Check the screenshot ... it shows the "properties" dialog, for the Opera app, that is specific to KDE Plasma. Adjust for whatever DM you're using.
The main point is to apply the string, " --disable-update" to the argument list (don't forget the leading space) that is added to the command-string to start Opera.
opera-upd.jpg