Going in the other direction, Dropbox will be ending support for macOS 10.12 Sierra in June 2023.
From Dropbox support:
We’re writing to notify you that in June 2023, Dropbox will be ending support for macOS 10.12.
Your files are still secure with us. In addition to supported Mac Operating Systems, you can still access your files from supported web browsers, iOS and Android apps.
As I read it, it means they are dropping support for the Mac app on 10.12 (not clear if existing installations will continue to work).
The web site will continue work fine - they explicitly say so. If they are using some feature not supported by Safari, you may need another web browser, but that shouldn’t be a showstopper, because the latest Firefox still works on Sierra.
According to a post in the Dropbox Community forums, the Mac app will stop working on macOS 10.12 Sierra systems on June 27, 2023. Your Dropbox folder will still be on your Mac, but it will stop syncing.
My recollection is that is what happened when Dropbox stopped supporting previous versions of macOS in the past, like El Capitan.
Unfortunately, it’s hard to recommend any solution other than upgrading to a newer version of macOS. Sierra’s last security update was three and a half years ago, and it’s only a matter of time before the alternative Dropbox clients will stop supporting it.
I presume that the Dropbox client will continue to be supported for a bit longer (maybe another year?) on macOS 10.13 High Sierra.
High Sierra should run on any Mac that runs Sierra, so unless a user has a specific app on your Mac that won’t run on High Sierra, moving to High Sierra (or newer, if possible) probably is the best option.
The main reason I never upgraded my MacBook Air from Sierra to High Sierra is because the upgrade forces a file system conversion from HFS+ to APFS.
I am pretty sure there is something wrong with this Mac’s SSD because when I tried to turn on FileVault (several years ago), the encryption process wouldn’t complete after several days (this is a small 128GB SSD), just sitting on my desk connected to power and doing nothing (not sleeping either).
And it wouldn’t let me turn FV off either, because the encryption was in progress.
I ended up wiping the Mac and restoring from a backup in order to recover.
So I’m understandably nervous about any other whole-file-system operation like an APFS conversion on this computer and won’t upgrade to High Sierra because (as far as I know), there’s no way to upgrade without converting the internal SSD.
I recall your saga from the old MacInTouch forums. I’ve kept a 2010 MacBook Pro running on Sierra in part because of your experience and also from inertia and a general sense of unease over the bugginess of the early versions of High Sierra. I use the old MBP solely for connecting to an old scanner in my home workshop, with the scanner output automatically going to a synced Dropbox folder. I’ll either try to eke out a little more service from the MBP by moving to High Sierra or just replace it with a basic Windows or Linux machine.
I installed High Sierra on an SSD that was formatted as APFS. I then did a SuperDuper! clone to an external spinning HFS+ drive. Upon completion, I reformatted the internal SSD to HFS+ then re-cloned the copy of High Sierra on the external drive to the internal SSD. Been running High Sierra using HFS+ since then.**
**But I never really used High Sierra. It was a required intermediate step to get my MacPro 2010 from Sierra to Mojave.