That instance just has a custom homepage written in React. The actual social UI is normal Mastodon with some color tweaks.
It is possible to use different frontends for Mastodon, though. Web apps like Elk can either run on a dedicated server to log into any Mastodon instance, or can be hosted by instance admins as alternative frontends.
If you look at any profile page, it's the classic Mastodon layout: https://veganism.social/@mascottus
The probably just customized the home page
If you really want something a bit less austere than Mastodon you can have a look at https://iceshrimp.social/
Thank you. iceshrimp looks good.
Don't like the Web UI? We test our Mastodon-compatible API against the following clients:
- Elk, Phanpy, Enafore, Masto-FE-standalone (Web)
- Mona, Toot!, Ice Cubes, Tusker, Feditext, Mastodon (iOS)
- Tusky, Moshidon, Megalodon, Mastodon (Android)
You can use any of those clients with normal mastodon, too
A community dedicated to fediverse news and discussion.
Fediverse is a portmanteau of "federation" and "universe".
Getting started on Fediverse;