kupietools
commented
3 years ago I found the problem. The restart had nothing to do with it.
It turns out one of my cables to one of my hard drives had gone bad, and an app I had specified as a protocol handler (https://github.com/johnste/finicky, set to handle http URLs) couldn't be found anymore, and SDA apparently deals with this by blanking out the first two tabs completely. I re-downloaded Finicky, and now SDA works as expected.
Leaving this open as an issue in case the dev wants to put in better error handling.
I've been using this for a while without issue, but two days ago I restarted my computer and now the the settings on the Internet and URI Schemes tabs are totally blank. Everything is gone.