Tumblr has a new setting to turn off

General settings > privacy > better recommendations (uses your search history to show you more posts)

On desktop Tumblr, the option was Settings > Privacy > Improved Search (uses search history to customize recommendations)

There was also an option to log into my “Privacy Dashboard,” which is apparently a place to see and manage how Oath (Tumblr’s parent company) uses your data to “improve and personalize your experience”:

The Tumblr Privacy Settings link on the Privacy Dashboard takes you to the normal Settings > Privacy page on tumblr, but the “Account Data” page you log into gives you the ability to “see your activity and data for each product you use on your account” (I just had a line of text that said “No data available to show for this account”), another link to the normal Tumblr Privacy Settings page, and a “Download Your Data” option.

If you haven’t already, I’d suggest logging into desktop Tumblr and checking this out. However, I didn’t see any options about clearing my data on the Privacy Dashboard > Account Data page. 

[OP and I are both posting on May 19, 2018]

When I tried to log into Oath to see my account data, I got this:

Seemed a little bit ominous to me. Did you guys trust them with your credentials? or does it just look ominous to discourage users to look further into it? I honestly can’t tell, so I’ll take your recommendations