Yep. Open source Dropbox is really Nextcloud - https://nextcloud.com
Given how many fuckups sync had over lifetime of it (at one point it basically asked for re-log every day, at other it just corrupted data/didn't finish sync), no
I use OpenCloud nowadays https://opencloud.eu and can really recommend it. It was easy to install on a VM and uses S3 for storage. No database needed.
Given how many fuckups sync had over lifetime of it (at one point it basically asked for re-log every day, at other it just corrupted data/didn't finish sync), no