I went this route. I replaced Dropbox with nextcloud and various backups with Duplicati on Hetzner a few months ago.

Nextcloud seems to be mature enough to mostly work. The sync issues are worrying but not a deal breaker so far.

As with Dropbox, it has a bunch of unnecessary but kinda neat extras. Except they don't work or don't work well enough to use.

Duplicati and Hetzner was easy and convenient. It seems to work from my non-rigerous tests.

For now, backups and sync for about the same price as Dropbox is a net win for little effort.

Because I control the stack and security, access, etc.

I pay like $7 for the server and $3.50 for the storage.

I plan on self hosting the hardware and just paying the electricity, which should be about half the cost per month.

I also host a lot of other apps on the box though like selfmade apps, VPN, nginx routing stuff