@Ben S.31 Have you put that two-partition system to the test? Because unless something has changed, I don’t believe Dropbox allows you to point a new software install at an existing Dropbox folder to avoid resyncing all those files. Every time I’ve ever re-installed Dropbox, it demands that I do a new sync to an empty folder.
And yes, you are correct, the new Dropbox version will not support non-boot partitions. The reason is that Apple has forced cloud file providers to store their files in a folder within your user profile. In some aspects this makes sense - think of a shared computer and the need to keep your personal cloud files private and separate from the other users - but it also creates a huge gaping problem for anyone needing to sync more data locally from their cloud provider than will fit onto Apple’s internal drive offerings (physically or financially).
Some folks here have mentioned just moving your user folder to an external drive (or in your case, the other partition), which should in theory relocate the cloud storage folder along with it, thus solving this whole issue. But poking around one will find many, many stories of this workflow backfiring on people, as any OS updates will break this setup and potentially lock you out of your computer. It’s super risky and, in my view, not a viable solution at all.
For now, one good option is to invest in a NAS and store your files there instead of Dropbox. This can completely bypass the need for on-demand syncing of local files to save precious drive space, and gives you so much more control over your own data. If Dropbox is important to you, Synology has a cloud sync application for their NAS that will sync with Dropbox, which I am currently using but honestly will probably not bother going forward. The reason is that this setup has so much storage available that there is no need to fuss with setting files to local vs online-only to save space, and the built-in feature set of Synology Drive is good enough to render Dropbox almost completely redundant. From here, you can back up your entire NAS to the cloud for protection via Backblaze, if you use their backup service which offers unlimited backup space. Not to be confused with Backblaze B2 which is like Dropbox and, because of the expanded feature set, is way more expensive.
