The Rust server tracking website rustservers.gg seems to be a relatively new one, as the Wayback Machine only shows captures of it since November 2022.

It's been used to produce graphs:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3354050834

http://web.archive.org/web/20221123134729/https://rustservers.gg/

Main index
- Servers
-- Server tracking websites