I found the following resource which resolved my problem.
I killed Syncthing, renamed .stfolder to .stfolder.bak and created a folder named .stfolder, then launched Syncthing.
Posting this here for others, since I wasn’t able to find info about the problem here before checking GitHub.
A little irritated–this bug has destroyed my battery over the past few days–which is the reason I initially investigated to find out Syncthing was broken. There’s no mention of these changes in the Android Store under What’s New. It would be nice if there was more information, or a link to more detailed Release Notes in that green box.