I used to have Opera 99.0.4788.31. Had issues with Zoom screen sharing, fixed by modifying /etc/sddm.conf and /etc/sddm/conf.d/kde_settings.conf to use x11 instead of wayland. After that after a restart, KDE Wallet popped up. I didn't use it before, and don't want to. Went to KDE Wallet settings and disabled it. Got logged out of Opera account. Logged back in, enabled synching passwords - did not work. Purged Opera, installed the 99 version listen above, still not synching. Checked opera://sync-internals - everything but passwords synched. Password synching states the following error:

Error: CleanupPasswordStore@components/password_manager/core/browser/sync/password_sync_bridge.cc:1056, datatype error was encountered: Failed to get encryption key during database cleanup.

and status Failed.

I'm confused because not using the KDE Wallet before (did not explicitly disable, but never popped up before) wasn't a problem, but after this change and disabling it, Opera cannot sync, so it must be related to that. The changes I made in both files are

[Autologin]
Relogin=false
Session=plasma.desktop
User=sagitta

which enabled using x11.

Is there any way to solve this without using KDE Wallet?