There are many possibilities, as it is not a pre-packaged solution.
For example, if you have Synology or QNAP, there are packages to sync with cloud providers, like Backblaze B2, Amazon S3, Azure Cloud Storage, etc. So if one of your syncthing sync instances (which you can make with few clicks) is such a device, with few more clicks you can choose your cloud platform and backup to that.
Or you can be using something entirely different. That's the beauty, you can use whatever fits your needs and budget, you don't have to fit yourself to limitations of one or two pre-packaged solutions. You can do something entirely different, e.g. if someone from your family also has some NAS, you can backup to each others devices and not rely on third parties at all. The possibilities are limitless.
Organizations already have such an admin, and workers can sync whilst they're at work. Not very difficult to set up, and saves tons of costs (although a NAS is a small initial investment to make it doesn't require much maintenance).
Individuals don't, but most individuals have no clue about the repercussions of hosting their plaintext data on Dropbox in the USA. Its a ticking timebomb.
2) you can run your own off-site instance, that can be hosted with your favourite cloud provider.