I tried downloading Dropbox's beta client (which switches to Apple's new APIs to get around this) and it's a disaster; the CPU usage of fileproviderd would stay

I tried downloading Dropbox's beta client (which switches to Apple's new APIs to get around this) and it's a disaster; the CPU usage of fileproviderd would stay at around 150% until I removed Dropbox altogether. This is, of course, Apple's fault for getting their API wrong and then forcing everyone to switch to their broken solution.