After upgrading to SpringBoot 2.7.0 I noticed that the Prometheus metrics "http_server_requests_seconds_count" and "http_server_requests_seconds_sum" were gone. All other metrics are still there.
I narrowed the problem down to the dependency to io.opentracing.contrib:opentracing-spring-jaeger-cloud-starter:3.3.1.
Whenever this dependency is added, the above metric vanishes.
I guess that opentracing somehow registeres itself as some kind of HTTP request filter to process incoming "uber-trace-id" headers and does this in a way that used to work but is no longer compatible with the way SpringBoot works.