Well I was wrong, I checked my network panel and it's definitely just thumbnails that it's fetching, I'm dumb I thought that only domains that served scripts ended up in the uBO matrix panel, I did a test and it does that with any third party content instead, static or not :p
From the community main page you tap the three dots top right of the screen and choose "block community".
It's definitely not only static content tho, I block third party scripts with uBO and it shows other instances domains in the blocked list.
Edit: I was mistaken, it's just images
You probably have an empty instance in your settings (eg. lemmy.ml but with no account under it) and were browsing the "Everything / All" feed, you went inside a post served "via lemmy.ml" and tried to upvote. Obviously it asks you to login in that case.
You can remove instances with no accounts by long pressing them. Also you can hide the everything feed from settings ;)
Also, Liftoff requires you to login to each individual instance to upvote anything from that instance for some reason.
Uh, I just upvoted you and this post from feddit.it using Liftoff
