I stumbled across this while doing some research and noticed there are no threads here about it. I'm late to the party on this but I thought if there are some people already on the case then maybe users from this subreddit might be interested in finding them to help with backups and hosting.

The NOAA is shutting down some of their online and printed services and they are removing that data from their websites. This project actually began in 2021 and is set to be completed in 2025.

So what is the RNC?

NOAA's RNC Tile Service (WMTS)

The NOAA RNC Tile Service provides standardized nautical chart tilesets for the public, eliminating the need for application developers to regularly undergo the cumbersome process of transforming NOAA BSB files into tilesets. It provides geo-referenced charts compatible with the Web Map Tile Specifications (WMTS) and Tile Map Service Specification (TMS). All tilesets are published on a weekly basis.

Original website (already deleted?): https://tileservice.charts.noaa.gov

Their annoucement:

NOAA will shut down its Raster Navigational Chart (RNC) Tile Service and the online RNC Viewer on October 1, 2021. The NOAA Seamless Raster Navigational Chart Services will be shut down on January 1, 2022. This is part of a larger NOAA program to end production and maintenance of all NOAA traditional paper and raster nautical charts that was announced in the Federal Register in November 2019.

Cancellation of traditional NOAA paper nautical charts and associated raster nautical chart products, such as BookletCharts™ and Raster Navigational Charts (RNC) will occur over the next four years and be completed by January 2025. More information about this overarching program to “sunset” traditional nautical chart products is available on the “Farewell to Traditional Nautical Charts” web page.

-- source

Why help with this project?

The abandoned nautical tilesets and paper charts have been replaced with GIS offerings for modern equipment, however these older documents were a failsafe for smaller vessels and operations. They may not have the technical know how to backup and retrieve this data otherwise.