

Sounds like Jellfyfin+Jellybook is your winner then. The server portion of audiobook or ebook hosting isn’t going to be giving you any game changing features. They serve files.
The client you use is going to make or break your experience here, so just go with the easiest setup on the server side, and then run through some clients to see what works best.
There are numerous automated systems for this, and almost every platform you use will have their own. Infiscal doesn’t seem bad, but I haven’t used it.
I always suggest engineers just use whatever is closest to their stacks instead of implementing something, UNLESS it’s going to cost a lot more money (looking at you, AWS).
Bitwarden/Vaultwarden+BWcli is also another workaround if you’re just using it for small projects.
Etcd can do value encryption, and Redia even, but you should really be looking at something that has solid RBAC, or ZTC rotation.