Super dope poster, lots of stuff about palestine and the middle east, occasional weeb stuff, IIRC they are a Marxist-Leninist
https://www.tumblr.com/guerillas-of-history
What it says on the tin, photos and short essays about various guerilla movements and leaders
https://oneterabyteofkilobyteage.tumblr.com/
Largely automated blog showcasing geocities pages. I really only follow this one for the soothing regularity of the posts.
There is still lots of good stuff on tumblr but it's not the place to be if youre interested in growing a following or making a name for yourself. Its a uniquely organic experience compared to the likes of xitter and instagram and I would argue that the site has gotten a lot better as the rest of the internet got worse*. Just so you know, the "for you" feed is based off of likes, follows, and your tumblr browsing history. It can be nice for finding new blogs but it if you go look at the blog of someone who leaves a shitty comment, you will start getting posts similar to what that person has on their blog.
*the 2017 porn ban was a disaster for online sex workers as tumblr was a remarkably safe platform for them. Also the moderators really like to ban transfeminine users for basically nothing. Other than that tumblr is pretty fuckin great!