Cryptomator [1] looks like it fits the bill for what you described. Seems to use a transparent mapped virtual WebDAV drive to make it usable. From my experiment

Cryptomator [1] looks like it fits the bill for what you described. Seems to use a transparent mapped virtual WebDAV drive to make it usable. From my experiments at least, it seems it should be usable by non-technical people without significant demonstration or training. [1] https://github.com/cryptomator/cryptomator https://github.com/cryptomator/cryptomator