So I decided to check on Reddit, but then there was a bug in Slide for Reddit (the app I'm using) which wouldn't show upvotes I made nor let me upvote anything. Previously I discovered a workaround where when you browse as a guest and go back to your account, the bug will stop for some time.
I decided to switch to a guest and back to my account too fast and, lo-and-behold, black screen.
I went to Settings -> Apps & notifications -> See all apps -> Slide -> Additional settings in the app, and now I see the settings. From here we can tap on About and /r/slideforreddit and we are now on the Slide subreddit.
Here I just used the search to search for the subreddit I wanted to go to and things worked for the most part. For an actual fix I opened /data/data/me.ccrama.redditslide/shared_prefs/appRestart.xml, and found this:
<boolean name="loggedin" value="true" />
<string name="name">LOGGEDOUT</string>Ah yes, being logged in and logged out at the same time. I just changed LOGGEDOUT to my username and now slide works again (but I switched to guest and back to my account SLOWLY to try to eliminate any configuration errors for now)