I had the same issue when I recently installed Opera Stable on Fedora 36 KDE. My native language is spanish, so I will use this language on this tutorial. Probably it will work for all Linux distros.
- Go to this route on your File Manager /usr/share/applications
- In this route, you find many files with .desktop extension. These are the icons you use to open the programs. Find the Opera Browser one (usually called opera.desktop)
- Right click on it and open with your favorite text editor (I use Kate in KDE)
- The first section must look like these
[Desktop Entry]
Version=1.0
Name=Opera
GenericName=Web browser
Comment=Fast and secure web browser
TryExec=opera
Exec=opera %U
Terminal=false
Icon=opera
Locate the line Exec
5. Add the text lang=your language after the word opera. Example for spanish
Exec=opera --lang=es %U
- Write the --lang flag in all places where you find Exec on the file
- Save the changes on file. Probably the text editor claim you for the super user (root) password. Type it.
- Double click on Opera icon. Your browser now opens on the language you selected.
The reason of this is: Opera is charged with all the languages, but the instruction that launches must be declared with the flag --lang to be opened on the language you want.
I hope I have been helpful.