ok I was able to clear it up mostly.
I deleted Gdevelop completely.
Rebooted.
Reinstalled Gdevelop 5.2.169
Opened a project.
Removed unused assets from the resources.
Saved project.
Closed project.
Ran Gdev update to 5.2.173.
Quit Gdev so update happens.
Reopened Gdev and opened same project.
Now the preview works again.
It’s weird because until I did exactly all these steps, when I’d open the project and poke around in the events, there were a ton events marked as errors, trying to call Gdevelop functions that didn’t exist anymore. All basic built-in functions like change object position were showing the events to be errors saying the extension for it didn’t exist.
It makes sense that maybe my desktop version was broke somehow by the update, but the fact that I ran the online only version of Gdev and opened a project from the cloud in there and had the same issues happening doesn’t make sense.
Oh well.
I’m having a new issue now that’s popped up (haven’t modified anything on projects so haven’t done anything to cause it) with importing sprites in the built-in Piskel but I’ll make a new thread for that.