A Synology NAS + Synology Drive has replaced Dropbox for me. Drive isn’t quite as polished, but I have effectively unlimited space, and it’s more private.
This also turned out to be a good alternative for me, although I kept Dropbox and had my Synology backing up everything to it so clients use Drive to sync to NAS then NAS to Dropbox.
Then my NAS died very prematurely, rather than buy another proprietary piece of hardware from Synology I muddled through setting up DSM in VirtualBox on a more powerful machine with xpenology. Using their operating system in a virtual machine lets you use their mobile apps too, about the only thing you can't do is use their QuickConnect service but there are other dynamic-dns services you can use in its place.
Also love my Synology NAS. I can connect my external services to it (Dropbox, Box, etc.) and wire those in as well. They make it painless and super trivial.
Then my NAS died very prematurely, rather than buy another proprietary piece of hardware from Synology I muddled through setting up DSM in VirtualBox on a more powerful machine with xpenology. Using their operating system in a virtual machine lets you use their mobile apps too, about the only thing you can't do is use their QuickConnect service but there are other dynamic-dns services you can use in its place.
https://xpenology.com/forum/topic/13834-virtualbox-dsm-62-ds...