Gave up trying to get the #LineageOS update to work, so now reinstalling everything on my phone (exactly the thing I wanted to do the day before a trip).
Good news: #Signal's backup thing works (the old one, I haven't tried the hosted one yet).
Better news: I could remember my PIN!
Slightly bad news: When I did the backups, it gave me recovery codes. When I did the restore, it asked for a passphrase. Apparently, these are the same thing (or, at least, the codes worked in the passphrase box), but it was pretty poor UI to ask me for a thing I had, but was given under a different name.
