Make sure you're using 121.0.5600.64. See https://forums.opera.com/topic/33033/opera-gx-update-released. The crash fix is likely for this issue.

@MrSmux try reset all setting to default, it should help. i guess.

Please provide the HTML and CSS for the testcase instead of just a pic.

do you use tailscale by anychance?

i notice opera doesnt work when i have tailscale enabled (i also use tailscale dns)

Do you mean one of the Subnautica mods from https://store.gx.me/mods/?search=Subnautica&tagAlias=desktop?

If so, you can just goto the URL opera://mods or open the mods sidebar panel and remove the mod. However, the effect that's causing issues with other sidebar apps might a shader from the mod or CSS from the mod. You can turn off just the shader at the URL opera://settings/shaders_settings or just the CSS at the URL opera://settings/web_modding_settings.

@Farligtt happened to me too, i still didn't find a way to fix it

@burnout426 i had posted this on a reddit thread as well and did some troubleshooting, the issue is fixed, thanks for your time though!