nginx

Kestrel on .NET 10 only speaks h2c on an endpoint set to HttpProtocols.Http2, and only to clients that use prior knowledge. Http1AndHttp2 without TLS silently falls back to HTTP/1.1, Upgrade: h2c is ignored, and nginx needs proxy_http_version 2 (1.29.4+, stable 1.30) or grpc_pass to talk HTTP/2 upstream. Checked with curl and HttpClient on ASP.NET Core 10.0.10.

Behind nginx and Docker, ASP.NET Core's ForwardedHeadersMiddleware silently ignores X-Forwarded-For and X-Forwarded-Proto unless the connecting proxy is in KnownIPNetworks or KnownProxies, and ForwardLimit decides how many hops it walks. The four silent-ignore rules, the KnownNetworks to KnownIPNetworks change in .NET 10, and a runnable repro checked on .NET 10.0.10.