@stefp I’m not sure it’s related to theme… two of my issues (1. My URL would randomly take people to the directory for certain devices and load properly for others, and 2., Post Kind plugin stopped working) seemed to have resolved itself with the new installation (well, I would hope so, since I took the raze-to-the-ground approach).
My biggest remaining issue is my Micropub plugin isn’t working. All the verification and authorisation goes through just fine, but when I try to post something using Quill or OwnYourGram, I’d get a “Your endpoint did not return a Location header” error.