As a user of Nextcloud (self-hosted), the most important feature for me is in direct conflict with OP's. I want my files stored verbatim as files on the server and accessible as normal files on a normal FS. No chunks, not encrypted, with the same directory structure as my cloud space. My main issue with availability and durability, not security. Of course I care about security, but losing my large collection of personal and family photos would be a much bigger disaster than some hacker having a copy.

When I tried Seafile, they had some FUSE implementation that allows access to the chunked files as a virtual FS, but I couldn't get it to work, so I dumped the whole thing. Nextcloud was so much easier to set up.

Having it this way makes it much easier to verify everything is readable properly and easier to replicate it to external drives and backups, also ensure things are accessible there.

Having different open source implementations with different tradeoffs is great, isn't it. That being said, I don't love Nextcloud's performance and some of its other design decisions, but it's the best I've found so far.