Are we talking permanent background tracking? Or sending a message "hey, I'm here"?
smiletolerantly
For manga, I've found Mihon to be nicest, by far, and it supports the API. For books, I am currently "stuck" on koreader on Android (which "only" supports OPDS-PS). I do most of my reading on a reMarkable currently, and that has no supporting client. Writing one is on my to-do list, but it's a bit daunting of a task....
Haven't had any issues in that regard, so can't really say, sorry. I have two folders (Mangas and ebooks) on my NAS, and in Kavita, created a library for each.
You absolutely can edit metadata, although I personally haven't had the need yet. I use readarr and suwayomi for "obtaining" books and manga, respectively, and what they come up with is usually just fine.
I went through essentially the same thing a couple months ago. Tried Calibre (and Calibre server) since everyone recommended it.
Really disliked it. Calibre is great for converting ebooks, but has shit management and webserving capabilities.
I ended up with Kavita and am super happy. On the web client, both management and actual reading are a pleasure. Any phone/tablet client supporting OPDS works perfectly to read/download your manga/books from the server.
And a select few clients go a step further, supporting Kavita's API, which allows for 2-way sync (effectively, syncing reading progress between all your devices).
Uhhhhhh
No? If they are hard, they are dried out. Chewy, sure, that's the fun; but they should be soft to the touch.