I see that a user can sync data:
Locally using Nearby Sync.
In the cloud with iCloud.
In the cloud with IBM Cloudant.
Have I covered all of them?
Can anyone comment on their experience with the last option. It appears there is a 1GB Free Tier, and then the price goes way up for storage:
https://www.ibm.com/cloud/cloudant/pricing
There’s also Apache CouchDB which you can install on a Mac or other computer on your network for free:
https://www.tapforms.com/help-mac/5.3/en/topic/apache
IBM Cloudant is good, but it’s a bit tricky to setup and also they have a 10 MB limit on a per record basis. So keep your attachments smaller than that and try not to put any images inside Note fields as that will balloon the size of records.
I’m using CouchDB on our NAS (QNAP) and I’m very happy how it works.