If using Kavita's builtin readers is not your cup of tea, you can use external readers over OPDS. OPDS is an open protocol to allow downloading and exploring reading content. OPDS by default does not allow for any progress tracking unless you use OPDS-PS with Kavita. What you find below is not an exhaustive list, but rather what has been tested to work with Kavita.
Have a suggestion for an app that we can connect with? Drop by the discord and suggest it.