En el menú de Opera hay un apartado que dice Desarrollo, dentro de él otro que se llama Administrador de Tareas, hay podrás ver la memoria y la CPU que consume cada pestaña y cada extensión. También puedes poner la url de esa página en virustotal y que la escanee a ver si está limpia.

The Twitch sidebar is not working properly, it doesn't show any channel.

In my experience in the past this related to ad blocking, maybe it is in this case, maybe not. I probably won't be back here but thought maybe that you can disable ad blocking or any extensions related to it. Hope it helps but if not, sorry and hope you get it sorted. Other common suggestions are to clear cache and flush your DNS. These might be helpful as well.