nostr:npub18mft426uwj82ezzzmh36z2t5exl8fwc8fj7x0pcwkj9wq2het6zqzqurv2 I thought you asked what instances use my UI.

Yes, it's just user interface theme for Mastodon. You can preview the demo for example on my instance: https://mementomori.social

You have three ways of applying it:

1) Use it via browser extension like Stylus to apply custom CSS

2) Apply it to your instance Appearance > Custom CSS

3) Add it as optional to your instance with core Mastodon modifications (not possible on Masto.host)