What? LOL you are accessing the Fediverse when writing this post.
I think you’re confused about what the Fediverse is. It’s comprised of a variety of software (mostly social media) that’s interoperable, meaning you can post on one platform, then read and reply from another.
You don’t need any app at all to access it. Apps are just frontends (user interfaces) to access the information submitted to the Fediverse.