Okay! So you first need to check /.well-known/nodeinfo to get /nodeinfo/2.0.json!

In the case of Pixelfed it’s in /api/nodeinfo/2.0.json

French telecoms tried the same a few years ago…

https://news.retiolus.net/readable_content?url=https://www.universfreebox.com/article/534255/faire-payer-netflix-youtube-et-twitch-pour-lutilisation-des-reseaux-si-on-veut-nous-donner-de-largent-on-est-toujours-daccord-declare-xavier-niel

https://mangrove.reviews/ seems to have a lot of potential, but is not federated as far as I know.