My wife uses the Amazon Kindle app on her Android tablet. You can use it for non-Kindle books by sending an email to a special email address for your Kindle account: https://www.amazon.com/sendtokindle/email.
Calibre is useful for this. It shows an easy to use "send to Kindle" button, and can convert books in ePub, mobi, etc formats to the format that works best in the Kindle app (AZW3).
If you want a web interface for Calibre (eg to run on a home server and download books when you're away from your computer), Calibre-web works well.
The problem with the send to Kindle option is email attachment size limit. For books it's fine but manga and comics are usually too big.
My Kindle is old enough that I was able to jailbreak it and install KOReader so I can just download from my Calibre server directly via OPDS. Otherwise if it's too big for email you'll have to do it over USB I think.
You can also use komf alongside komga/kavita to just scrape metadata automatically upon import. A bit finnicky to get going (a tampermonkey script is required to give it accessible setting on the komga page) but works very well and even has a gui for identifying results and selecting the correct option if the auto scrape fails similar to jellyfin
For the actual reader part I just use komga as a server and read through Mihon (one of the tachiyomi forks) on my ereader mostly. occasionally I’ll use paperback on my iphone (although recently I’ve been trying Tachimanga, which is basically an iOS tachiyomi fork). Loads library, can sort by tag/library/date added, reads most things very well, can sync read status with the komga server (and/or manga updates or whatever), etc.
Thanks for this, I have a similar setup and looking to migrate from Kavita -> Komga + iPad reader. For Paperback, does syncing read progress actually work to/from Komga? In the Komga instructions for syncing it directs me to install a custom Paperback tracker that only works for v.0.7 (and Paperback is currently v.0.8).
Kavita+ is for features that have an ongoing cost for the devs. They have to spend their own money for running the servers hosting the backend of the k+ features, as well as for access to APIs. They are not features that could have possibly been free.
Also, I'm not sure why an unobtrusive donate button is a downside to you..
There is Komikku for linux though it's kinda limited to sources it supports. Komga is a nice self hosted option with support for Mihon and all the tachiyomi forks for android. There is a tachiyomi fork called Komikku (different from the linux app) that I like.