You can start your own F-Droid compatible with Repomaker. Advanced users can also start a repo using F-Droid CLI tools.
You can't submit apps to appiverse.io directly. You can either try to submit your app to one of the repositories already listed on appiverse.io, or you can start your own repository.
Not all existing repositories accept submissions, and many of them have critierias your app will need to meet to be legible for inclusion. If you want your to be available in F-Droid client by default you have to submit your app to F-Droids repository .
If you've started your own repo you can use our form for submitting repositories to get listed on appiverse.io.
You can use our form for submitting repositories, to submit your F-Droid compatible repository of apps. If you want to submit an app, you'll need to submit it to an existing repository.