Material design 3 was released in 2021, so I'd call that somewhat modern and is the latest release of Material design. Unlike Apple's design language Material design is also meant for the web.
There is already a Invidious interface for Apple devices, but ofc isn't a web interface like Materialious.
Thanks for your interested. Currently this is just a alternative frontend for Invidious. But I am open to integrating other services into Materialious.
Yes anyone can host Materialious on their own server! Does require you to host Invidious too.