6.1.0 breaks iframe tags in TextArea with Formatting set to 'None'

I have a TextArea field with Text Formatting setting set to ‘None’. This has allowed me to embed iframes (e.g Soundcloud videos) just like is described at https://expressionengine.stackexchange.com/questions/8889/textarea-turning-iframe-tags-into-special-characters

Prior to running Expression Engine 6.1.0, this worked great (I was on 6.0.6)

I upgraded to 6.1.0 today and now my iframes are broken and the HTML tags appear literally on the page with ‘& lt ; iframe’ instead of the tag. (I have added spaces to avoid the forum formatting it properly!)

Is this a regression?

Is there a way to be able to embed iframes again in a TextArea, or should I use some other field type? I tried the Rich Text editor but couldn’t see an option to create an iframe that way.

Thanks!