They are already selling data to midjourney, and it's very likely your work is already being used to train their models because you have to OPT OUT of this, not opt in. Very scummy of them to roll this out unannounced.
Account Settings -> Visibility to find the setting on mobile
They also quickly put out a long “tumblr is dedicated to protecting the data of its users blah blah blah” post. Then why isn’t the setting to opt out turned on by default then hm???
(It’s because nobody would turn it off obviously but still. Ultra scummy)
YO. IT'S IN YOUR INDIVIDUAL BLOG SETTINGS, RIGHT HERE.