That was weird. Suddenly my Dropbox basic went from having 5.3 GB of free space to being full. I worked out how to permanently delete stuff, though, now I have 5.4 of 7.4 GB free. No longer keeping the Epichrome salvage file in Dropbox, that being expanded there filled the spare space, moved that zip file to OneDrive, where I have over 230 GB available.