How have I not heard of this? Doing a quick HN search I see it's been posted multiple times over the years, but with minimal uptake.

https://hn.algolia.com/?q=https%3A%2F%2Fcryptomator.org%2F

Perhaps the problem is that the privacy conscious have already deplatformed & do their own syncing to private cloud, whereas the others are still using the platform & don't care as much.

I'm in the first group, but have become increasingly weary of keeping servers online (I self host everything) & I'm see a lot of promising results in Crytomator... but there's one inevitable gotcha: those very platforms can cut you off at some point in the future. So, you'll need to multi sync across multiple platforms for redundancy.

That said, cryptomator looks good!

And at least on iOS it works nicely with the native file system

It's only open-source on desktop.

rclone is good too, particularly for people using the command line, and supports client-side encryption.

https://rclone.org/