

Not really self-hosted, but I set up obsidian with syncthing and am going to transfer all of my notes from book stack to it and let bookstack be more organized documentation and obsidian to be a big scattering of notes and tags and such. I tried it with bookstack, but the flow was too much of a barrier for me to use it consistantly
No, ssds have a ton of wear leveling where data is shifted around and not deleted. Deleting data wears out the SSD, so it is held as much as possible with the controller. SSDs are like 10% bigger than advertised just to prolong the life.
Even if you write the whole thing with random data then zeros, it will still have blocks in unaccessible (to normal users) places that contain old data.
Always best to use disk encryption or keep any sensitive data in filesystem encryption like plasma vaults or fscrypt.