I just tried copying the extension address from Vivaldi and pasting it in Opera and it loads Group Speed Dial, so the extension works but something in Opera is causing it to crash on browser exit.
EDIT:
Seems like the default address created by Opera for GSD is the issue. It's different than what Vivaldi has. once I added the address from Vivaldi to Opera I went into Opera's settings and saved it along with Sonarr calendar and Goole as my start pages. When I closed and relaunched Opera I had all my GSD groups. I suggest leaving this thread here in case others run into this issue.