You can see it after clicking on the onion lock icon > Connection is secure > ‘Verified by,’ which indicates the provider. In the case of the BBC, it’s Degicert, for example, the same organization that also provides SSL certificates for regular sites.
@Lind @Protium_serratum I don’t know why I’ve started to see that warning for more and more websites. I also see it on Dread now. Can you check if this is normal by visiting the website, or if I am being targeted?